My simple non-football coach opinion is that the staff want Collins to focus on one spot in camp, not get overwhelmed... and partly to give him a shot at starting. I think we all recognized when he was drafted that Collins had a shot to push Leary out of the lineup. Hasn't played out that way, but I suspect that once TC is over, and Collins is officially named a backup, that they can slowly work him into other positions. I mean if he's not starting, then it would make sense to have your best backup OL be able to work into G or T in case of injury.
The injuries may have somewhat diverted Joe Fan's opinion on whether that's a good idea. We see Free sitting out and say, they're really going to go with Weems there if Free is really injured? Why not gain some position flex with Collins? It make sense logically, but at the same time, I think it would be smart of the staff to not change directions so quickly with Collins if my theory is correct... Have a plan and stick with it until you're forced to do something else.
If Free does miss time in the regular season, and Leary wins the LG job, then you can work with Collins at T during the weeks. I suspect Collins can at least give us something there, even if he doesn't have a full camp of reps there. If Weems can't do shit, Collins could probably be at least a serviceable replacement. He wasn't a consensus top 10 talent because he was seen as a G.