This would not be the first time some vet scared the bejeezus out of puppy buyers. Do not blame those people.
My keeper pup last year developed FCP when she was around 6-8 months old. She was on rimadyl for a week and crate rested for a month. It did not help. I ended up having the arthroscopic surgery done. The recovery period is around 3 - 5 months, depending on how good you are about keeping the puppy confined. If you increase walks too early or let them loose too soon, it can double the time needed to regrow cartilage. Periods of activity can destroy the cartilage as soon as it starts to grow back.
After the surgery, the surgeon saved the fragments he removed, put them in a small vial and gave them to me. It didn't take a whole lot of imagination to see the piece of bone could cause pain and swelling in the joint. The surgery will not reverse the FCP. The joint will never be 100% normal. The goal of the surgery is to lessen arthritis over the dog's lifetime.
I first took the pup in because of the lameness. My regular vet examined her and took x-rays and thought they did not look quite right. After the course of rimadyl and month of crate rest showed no improvement, we consulted the ortho vet. Physical exam, more x-rays and evaluation of the lameness all pointed to FCP.
I have a 7 year old male who had bilateral FCP, arthroscopy at 14 months, bilateral.. Dr. Kurt Shulz, our surgeon said, let him be a dog, and I have, and he competes in Rally, agility, obedience, hunt tests and is very very sound, no sign of arthritis yet.. he will continue to be a dog, without worry...
Well, the orthopedic surgeon says there is cartilage regrowth. It is a very slow process and the new growth is fragile, which is why they must be kept quiet for so long.