The hosts on outside Xbox also called FL4K a he. Putting aside the "outrage to the outrage" of misgendering FL4K, if you really want to make a non-binary trans character, you probably shouldn't use a robot who has by far the largest build of any character in the game, has a distinctly male voice, and is played by a male voice actor. Someone who looked closer to David Bowie when he was flirting with androgyny would be a good design for such a character. Not a robot with only male features.
As I said in another thread, It'll be interesting to see and hear how FL4K's gender is represented in the actual game. So often, it seems people (both developers and consumers) make a big deal out of "did you know" type details that aren't even found in the game itself.
Did you know Solider 76 is gay? Did you know Bloodhound is non-binary? Did you know Profit from Black Ops 3 is a homosexual? No. I didn't know, and I didn't care, and none of this is even found in these games. And if Borderlands 3 handles player characters like Borderlands 1 and 2, FL4K's pro-noun might as well be "vault hunter" anyway.