If another tight end is injured somewhere down the road, it might be nice to have an experienced guy, like Quarless, available. Nothing requires you to bring them back. Anyone really valuable they will want back as soon as possible, 6 or 7 instead of 8 weeks. I doubt they will use it for a starter, unless they really expect him to be out 10 or 12 weeks, but have hope that he might get back sooner.
Regardless of the player, since they will have at least four games in the books by the time another player might be injured, the usefulness of the designation will be gone very soon.