Without knowing the specifics, I don't know how we can conclude this is entirely unrealistic.
Say you're a good HS basketball player who wants to go to a good team and play for championships, and wants to stay close to home. You know you might scratch the top 1000 players in your class, and some folks think you can play D1, but you have no delusions about playing pro ball, at least not in the states.
A high level, local D3 college has invested a lot of time and resources into recruiting you, they've got a great coach, they're playing for championships every year. They've pretty much concinced you, but regulations prevent you from signing with this team until the end of the school year. Toward the end, a mid-level Big 6 school, who has lost out on all their targets comes calling, offering a scholarship and a chance to sit on the bench for 3 years, and maybe (if they don't cut you) you'll get some PT as an upperclassman.
Is this a Slam Dunk? Probably not. The championship level D3 matches some important preferences, and the chance to "be the man" on a high quality "small pond" team is enticing to a lot of guys who know they'll probably never get a paycheck for playing basketball.