Sometimes that is not the case. Adding footjob, ANAL COWGIRL, armpit, whatever, doesn't affect the game as long as it is optional, in my opinion games should have an option to block content the user doesn't want to see (For example, I'm not interested at all on vaginal sex).More sex options is always good as long they are optional, so people can aways choose what they enjoy and avoid what they don't. I personally like to vary even with things I don't enjoy much, I like having options, feels more real than being stuck with vanilla stuff.
However, there is content that even as optional affects the characters, if the bot had a route as a cheater and enjoy it, that would change the context of her character even if the content was optional, that would make her capable of being an awful and distasteful being who would eventually do something like that in the context of the lore.
TLDR: Its okay to add optional content where the bot just tries to please you and stays in character. Is not when this optional content re-contextualize her character.