FAFSA, I think you're confusing the bridge/conditional admit program with something that is elective.
Some students who might appear to be marginal admits for fall (doesn't mean they are, just means they maybe come from a school board known to be weak, or might have had some other glitches in performance where Umich just wants to make sure they have tools for success) are admitted "IF" they first attend the summer bridge program and pass those courses.
You cannot ask to do this. Umich offers it to a few students who either come from challenging backgrounds, or underperforming school boards (Detroit, a lot of times) etc.
Hope that clears it up.