I don't care a whole lot either way, but for argument's sake; it
is possible to combine the two. If we think of it as sexual conditioning (corruption tag) of an initially dominant futa. Cumming with her cock, in spite of it being completely neglected, seems like it would be peak degradation, if that's what you're after.
The in-game conditioning process could begin with cumming with her cock (in spite of it being neglected) from vaginal/anal stimulation. Her cock "swaying back and forth pathetically" (example from Priapra being fucked by goblins, in the game
A New Dawn by WhiteRaven), and then cumming uselessly on the ground. From there it could continue in the same way, or gradually transition to her no longer being able to cum with her cock.
Just saying that it's possible. I guess it
is a little weird that neither Valerie nor the storytelling mentions Mia's cock in the sub scenes, even though its presence is kinda obvious and clearly the "elephant in the room"