It’s one of those nice euphamisms that prevents us from needing to cross our legs in a universal protective gesture. I knew one lady who took great joy in refering to the same operation on a male cat as getting the cats berry’s whacked off and then watch all the men cringe.
A lesbian I know once waited until she had a big crowd of people around before announcing, “I just took my kitty in to have his little balls snipped off.”
Maybe half the universe. Actually what they do to the female cats is major surgery: ovariohysterectomy. The males have it easy. Female cats take a lot longer to recover.
Having lost one gonad I can relate (clutch abdomen, groan, sprawl).
IMHO people say “fixed” because they can’t remember who gets spayed and who gets neutered.