The reader is meant to understand that Grace feels a general social disconnect from the Project Hail Mary team stemming from his poor self-confidence

The reader is meant to perceive his total lack of awareness with regard to how highly he ranks in the project’s hierarchy of power

These two points, having previously been established, are both cemented by the scene. Grace is uncomfortable being enlightened to the details of DuBois and Shapiro’s sex life, and he doesn’t seem to grasp the fact that both scientists view him as a superior. It’s heavily implied that DuBois initiates the conversation because he feels the need to report developments in his workplace relationships to a higher-up, and I firmly believe this to be the case—he comments on the prudence of informing Grace on the subject—but that motivation alone doesn’t account for all of what he says. The way I see it, just about anyone alive (regardless of their personal stance on romance or sex) would feel awkward in Grace’s shoes, which begs the question: Why did DuBois and Shapiro both overshare so brazenly?

The first possible interpretation: Knowing that their relationship is doomed, they’ve elected to completely set aside social decorum in the interest of enjoying their time together to the fullest.

The second possible interpretation: They wanted to test Grace’s receptivity to becoming their third.

Stay with me. We can infer that the conversation was premeditated—DuBois launches into it very suddenly, and the first thing he does when Shapiro returns from the restroom is update her on the basics of what’s been said. This is clearly something that they discussed sharing with Grace in advance. Furthermore:

DuBois gently counters Grace on the merits of entering a relationship under the otherwise bleak circumstances

He’s overly blunt and forthright about specifics, such as the lack of need for condoms and the fact that he and Shapiro have both undergone thorough medical examinations

When Grace demonstrates disinterest, DuBois drops one last hint, which is what really sealed the deal for me: “It’s quite pleasurable.” Grace still doesn’t take the bait, so DuBois begins to back off. After briefing Shapiro on the status of the conversation, he deftly changes the subject by pivoting into science talk, but Shapiro gives another independent push: She interrupts the beginning of Grace’s lecture to openly invite DuBois to sex after the lesson, and then they both look at Grace. Grace interprets this gesture as them being “ready for their lesson,” but I would argue that it’s really a classic case of unreliable narration. He misses the cue.

I imagine that at this point, Shapiro (like DuBois) is willing to give up the cause, but we get one more small tidbit of insight: Grace asks (out of what I can only assume is morbid curiosity) if DuBois sticks to his convention of using Shapiro’s professional title during sex, and they both answer affirmatively. Just prior, we hear Shapiro address DuBois by his first name, and prior to that (directly before introducing the topic of sex), DuBois encourages Grace to address him by his first name as well. Granted, that encouragement was prompted—Grace makes it known that he would prefer to drop the formalities in private settings, given that he views the three of them as equals—but DuBois is shown time and again to be someone who highly values professionalism in and out of the workplace. He politely declines Grace’s invitation to address him as Ryland.

Power dynamics seem to play a role in his sex life with Shapiro, as evidenced by her disclosing that she “kind of likes” his use of her title in the bedroom. With that in mind, I don’t think it’s a stretch to conclude that they would both be into the idea of incorporating (what they mutually perceive to be) actual power dynamics into the relationship through the inclusion of Grace.

Circling back to DuBois’s staunch professionalism, I would cite that as further evidence that he’s coming on to Grace in this scene—discussing the minute details of your sex life with your boss is about as far from professional as you can get. Much of what he says is superfluous and irrelevant to the goal of reporting on the existence of a sexual relationship under obligation, unless you factor in the possibility that an obligatory report wasn’t his only goal.

As a final note, I remember the DuBois-Shapiro scene in the movie sticking out to me even upon my first viewing, just because of how oddly it plays out: The two of them are cuddling up at the pre-launch party, and DuBois seems to intentionally make eye contact with Grace from across the bar—who, being caught off guard and slightly uncomfortable, nods in acknowledgement and looks away. I wasn’t sure what to make of that prior to reading the book, but now it stands to me as a reference to the existing undercurrent between the characters in the text. In both versions, DuBois and Shapiro make a bid for Grace’s attention, and Grace is unreceptive. Given that no pre-launch party scene occurs in the book, I have to conclude that the inclusion of this detail in the movie was intentional and carries subtextual significance.

Obviously, if we take this interpretation at face value, it’s more fuel to the fire that is the aroace reading of Grace. It can be used to argue that he rejects amatonormativity on all levels—not just in his scant experience pursuing longterm committed relationships, but in his failure to so much as entertain the idea of a fling or friends with benefits arrangement, even when an easy opportunity presents itself. Romantic affairs never seem to cross his mind. He’s oblivious to the way his relationship with Stratt is perceived until confronted on the subject by DuBois, and he’s quicker to accuse her of sexism upon learning that she sought an all-male team of astronauts than he is to put stock in her actual line of reasoning. If DuBois and Shapiro were indeed trying to make a move on him, it’s no wonder that it flew over his head.