No, they don't. What you're saying is theoretically possible, in fact the Ravens have a history of IR'ing young guys with phantom injuries to prevent other teams from snatching them up off the practice squad (can't think of an example off the top of my head, but I know it's been discussed on here, maybe someone who's been around longer can help me out). In order to DTR a guy, he has to have been on IR for at least 6 wks, and then you have to make a cut on the 53 to bring him back.
The problem with that is you can't practice while on IR, which is why the PS is so important for developmental players like Ochi and Reynolds. You can prevent PS players from getting poached by activating them to the 53 but then you still have to make a cut elsewhere to make room.
Could make for an interesting situation with Elam and Pitta, though, who both seem to be at a huge fork in the road with their careers