Some of this does happen but not always for the reasons that you might think. For the Ivys (and Stanford) some high academic kids who might not be starting material but are excellent players nonetheless are recruited in order to help with a teams academic profile. It allows some of these teams to take some more athletically gifted kids at the expense of others by providing an academic offset. But these kids are likely more than qualified academically.
People don’t realize just how important these recruits are. This type of player is in every major program and many people wonder how they got there because they just sit on the bench every game and they don’t travel to away games. They are recruited and generally understand their role going in.
Practice players are incredibly important to successful programs (their teams need to practice against quality opponents every day) and they are not easy to recruit. Using volleyball as an example a kid good enough to challenge the Sanford volleyball team on a daily basis is good enough to start in the Ivy league. Finding kids willing to do this isn’t easy; if they have reached that level they want to play.
Practice players exist on Ivy league football teams and in most major sports programs. I think that if you look at the roster of a team and there are 3x as many players on the team as are on the field/court you have some practice players.
I personally know kids who went to Columbia (football), and Stanford (volleyball) knowing that weren’t ever projected to be starters. They valued the educational opportunity more than starting and had great experiences.