The news isn't surprising and isn't necessarily significant because the Patriots can remove him from the PUP list at any time. But it does show the Patriots want to remain cautious with Welker's surprisingly quick recovery from reconstructive knee surgery.
The PUP designation, however, prevents Welker from practicing with the team until it's lifted. That shouldn't be a problem for a hard charger such as Welker. He'll be fine working out on his own until the Patriots are sufficiently satisfied he's ready for full-go workouts. Welker can attend team meetings and rehab at the team's training facility.