They've moved him all over, this isn't anything new.
Last year in preseason we even had him playing special teams in the preseason games. Then on the practice squad they had him at safety, WR, QB and various punt return positions.
I don't know why anyone is surprised about this. He isn't a legit QB prospect but he has size and athletic ability. I guess they like his work ethic and are just trying to find him a way to be a contributing football player.
There are a few theories I see here:
1. The Belichick mimic of Edelman, Troy Brown, Mike Vrabel where a good player can play multiple roles. Showers is not big, fast or clever. This theory would be like the 12 personnel mimic, the Romo is a pocket passer mimic and "we want to be aggressive at the end of games" mimic. All well below his capacity and football intelligence to make successful. Plus Garrett doesn't understand that mimicking is not simulating: true mimicking would be succeeding in accomplishment. He thinks he mimics Jimmy, Coach K, Pete Carroll, and Norv. It's like just senseless costumery.
2. The "make use of the back up". Sanchez may be the backup, but if they feel Showers is capable of DB and backup QB, maybe Sanchez is just a waste of a roster spot. If he can only play backup but Showers can supply two or more roles, then maybe they can find another pass rusher, oops, no they would get another tight end.
3. Just likes Showers. Like Kellen Moore or Matt Johnson or any of his summer campers.