I can understand not exercising a puppy until it is exhausted or too tired but I can not see the logic in protecting joints by witholding walking.
Surely strong muscles and ligaments protects the joints?
If I give my puppy restricted exercise in line with the 5 min rule he then runs around the house like a loon, jumps on furniture etc and is crazy.
If he has a longer walk he sleeps and is probably less active over all.