I guess it depends on what the player was told. I was always under the impression if Iowa offers a scholarship and the player verbally commits, Iowa will honor that offer.
Now if a player is told that Iowa is offering 1 scholarship to 3 different players, and whoever commits first gets the scholarship, that's different.
Also if the player is promised only a grey shirt, that's basicly a promise he will get a scholarship when 1 opens up later.
Players that are preferred walk-ons obviously are promised nothing except a chance to compete for playing time and maybe a chance to earn a scholarship.