I mean, he seems to just suck as an NFL player so it's no real loss. If they're planning to move to Maye at some point soon though I think it does make sense to at least give him a chance to play with Maye. His only positive trait is straight line speed yet they've never paired him with a QB who can throw deep. Maye would be the first he's played with here.
Again, Thornton seems to not be any good but it's not like he'd return any value to miss out on, no one else in their WR room has any real deep speed, and it's not like they have such a deep roster that they couldn't find anyone else to cut. I'd give him a shot to play with Maye, even if just so Maye can have a speed guy to throw to and work on that part of the route tree.