22 spots are already locked up for presumed starters, and while those starters may change, due to injuries and other factors, the top backups are also assured spots in the lead-up to preseason as well. For the Washington Redskins, depth is important now more than ever, and so depth players receive a guarantee.
The foundation of the roster is inherently large, and it leaves only the scraps for the players on the roster fringe to fight over. These fringe players have only a few weeks to make their cases to the team, before a select few are kept for the season, while the others are discarded, until injuries send other teams calling.