Exactly, because it seems like a very basic and smart idea to easily add content that pleases people.
The key being how it is presented. I'm not even suggesting it show fantasy of straight-up penetration and cumming all over her face, lol.
People can put 2+2 together. The right angles and the right character thoughts (dialogue) during the fantasy can show it without showing it.
Which, again, has been done already so it's not some new concept. Nobody sees Sophia as having fucked the mob brother but we technically saw it in a fantasy.
It's how it is presented that's key and I think it wouldn't matter who you did this with if done right. It adds content quickly, gives fans wanting more sexual content some content and doesn't spoil the main event (when it arrives in the year 2038).