in my opinion there are 4 possibilities:

Rocky is a freak because he spent half a century alone in space, +-

Rocky spent half a century alone in space and survived because he is(has been) a freak -+

the two previous assumptions combined, aka he was a freak before and became even freakier after ++

Rocky is not a freak and has not faced any major changes in his character and he is Normal™ (booooringgggg i dont ljke it)--

the same can be applied to Grace:

Grace is a freak because of all thats happened to him somewhere between starting to work for the project and the end of the trip to Erid +-

Considering he's majored in microbiology (as far as i remember) and taking into account that a big part of scientists in any field are freaks(said lovingly), Grace did not go crazy after those 4 years on a tiny spaceship because he has been a freak the whole time (<-said in Sam Reich's voice) -+

both of the above, has been a freak and became freakier ++

neither, a boring option i will blissfully ignore

and all those possibilities are only for these two separately, combine these and you get 16(4²) different dynamics! and i love all of them (okay maybe only 15 of them there is no way both of them stayed normal)

and thats why i think any and every gracerocky interpretation, from purely platonic soulmates and up to the freakiest shit you could find on ao3, is valid due to the characters' origins AND the things they went through

Ps. dont get me wrong, im not fun police and im certainly NOT saying that some interpretations are completely invalid and i hate people who have fun, quite the opposite, it's just that there are a shit ton of their relationship interpretations that are a lot closer to canon than to fanon. if there are any grammar mistakes i dont care i have no respect for this language