You can't control who or what you introject from most of the time. This goes for fictives, factives and the alters who just pick up a multitude of traits (from the media they consume, the people they meet or see, the environments they're in... etc).

Also you don't control the way you introject either. For fictives, you might not start off as canon-compliant (or identical to your source). For factives, especially ones of your irls, they're more commonly just imprints of a certain side to them.

And then even if you do have an introject who's either canon-compliant or highly resembling of the person in question, nobody's identity will be stagnant. All it takes is time and events/experiences that will shape the way you act, the way you identify, your preferences... basically the normal human experience.

I think some people forget that introject alters are their own people, more or less. They will turn out the way they turn out.

"Nothing can live up to promise / Nothing can stop its narrative (you)" fits here imo (lyrics from Transgender by Crystal Castles).