Welcome to the board, Bill!
There may be some knitting and regrowth, but limiting exercise at this point is still critical to good healing. It takes much longer than a few weeks for the bone to be solid. But he
could be showing signs of healing this quickly.
The only experience I have with a pelvic fracture is with a neighbor's dog, also hit by a vehicle, also broken in three places. But in his case, the whole pelvic girdle rotated and skewed. Unfortunately, by the time the regular vet referred them to a specialist (about 3 weeks after the accident), the bones had begun to knit and the hips were deformed permanently. So there is definitely some bone growth by week 3. But the bones won't be solid for a few weeks yet, so as tempting as it is to release him, keep him confined until you get the okay. Good healing now will help prevent problems with arthritis later in his life.
I hope he's healed up and back to his happy-go-lucky golden self soon!
