This is actually a slick move by the Giants. After he was waived/injured by the Giants, LaCosse cleared waivers and was placed on IR. The injury settlement actually releases him from IR and makes him a free agent available to the other 31 NFL teams. If he is hurt, however, teams are not going to use a 90-man roster spot on an undrafted rookie who can't practice. That's likely why LaCosse got waived in the first place.
Should no one pick up LaCosse, on whom there will now be no NFL game film as he will not have appeared in a preseason game, NFL rules state that the Giants could re-sign him after Week 6 of the regular season. So, this move actually makes it possible that LaCosse -- impressive in the spring -- could actually be a Giant at some point in the 2015 season.