The problem with bottom of the roster and practice squad players is they never get on the field for games. At least in the USFL, the player gets to play, and maybe develop. Hall of Fame QB Kurt Warner is a great example of a guy who was able to develop in the NFL Europe league and Arena League in the 90's, getting to start full time. This was after getting cut by the Packers when he signed as an undrafted free agent in 1994. The famous story about him stocking groceries when he got a call from the Rams is legendary. The next thing you know, he wins the NFL MVP and the Super Bowl as a first year starting QB for the Rams in the 1999 season, and goes on to a HOF career.
Getting playing time can help develop a player more than sitting on the bench and getting a few practice snaps during the week on an NFL practice squad. The NFL really needs to get a developmental league - as shown by how impactful both Turpin and Aubrey have been after spending time in another league actually playing.
What we do know about Harvey is that he led the USFL in tackles and was considered the best linebacker in the league this past season. That is worth a look, no matter how snide and cynical fans want to be about the front office.