I find Weir's paratextual (not in the book but he talked about it to some fans) status-based binary pronoun system for Eridians really interesting.
But. I really like they/them for Adrian.
To not contradict one but still maintain an Eridian equivilence for the other, I have some ideas.
The status-based binary pronoun system developed as only a feature of some language families on Erid, including Rocky's native tongue (native hum?).
Which means that there's room for Eridian languages that have only one pronoun, or more than two, or zero! And perhaps Adrian's native hum is one of those languages, and their pronoun is just borrowed into Rocky's hum to accommodate for cultural preference.
Alternatively, Adrian's native hum is the same as Rocky, but they're an anarchist type who disagrees with distinguishing people by status, and thus uses a neopronoun that does anyway with communicating status.
Or maybe Adrian's native hum is still different, but their contrasting pronoun systems make a them even more motivated against status-based pronouns.
If you take in James Ortiz's personal headcanon that Rocky and Adrian were matchmade together in an arranged marriage, maybe it was across ethnolinguistic lines? Fun to think about those worldbuilding implications.
Also it would be interesting if Rocky's Eridian language also had different first person pronouns that communicated status as well. It could be similar to modern Japanese, or historical Chinese's honorifcs.
In Japanese, 私 (watashi) is the default polite, gender neutral first person pronoun, but also women tend to use it in broader casual contexts than men; it also has an alternative pronunciation (watakushi) written identically that is even more polite; a derived form, あたし (atashi) is casual and feminine sounding in modern day. 僕 (boku) is the boyish, not polite but not rude pronoun that gives a masculine, soft and youthful sound. Compare that to 俺 (ore) which is also masculine but overtly crass and casual, usually used by men in casual settings among other men.
In Chinese (using Mandarin pronunciation) the default first person pronoun is 我 (wǒ) and it is totally gender neutral. However historical (and somewhat into present) Chinese has used various honorifics as a first person pronoun depending on their status.
在下 (zàixià) is a masculine honorific used in first person, but literally means "existing beneath (you)", which elevates who is being spoken to.
本人 (běnrén) is a gender neutral first person honorific literally meaning "this person" or "my own person". It's not particularly a humbling honorific, but is considered more formal that 我.
孤王 (gūwáng) is a masculine royal first person honorific meaning "lone king" or "the orphaned king" in deference to the ruling king's father who is deceased. This was only used by a king in that context.
哀家 (āijiā) is a feminine royal first person honorific meaning "(this) sad house" and was used by the emperor's mother out of respect for her late husband, the former emperor.
Looking at real life human examples of how such pronouns and honorifics can work makes wondering about Erid's languages and cultures, and Rocky's in particular, extra interesting.