I do see what your saying, it is just the books have a secunit clearly not looking like any gender. They have skimmed over Muderbot's disgust of gender and sex, but in the books it is constant theme. It's visceral.
To have them be genderless is only half way, as secunits, in the books, also look genderless (and not human).
Skarsgård, for a dude, is doing as good a job as he can. Not many known actors could visually do what I'd have preferred, and also can do a ungendered voice. (Any?). I know it's easier to do it books and realistically they needed a well known actor to pull people to the show.
It's just...just.... That's not my Murderbot!
I think commercially, they needed a known actor and who can not only look genderless, but sound it? It is easier in books.