There are many yorkies with luxating patellas. Yes, the knees do pop when manipulated manually but that alone does not mean they must have surgery.
I strongly suggest that you go to a board certified orthopedic surgeon for a second opinion. The trend these days is away from all of the surgeries that used to be done on these pups. If they are not having problems ambulating and not having pain, I don't consider surgery. That is what my board certified vet suggests.
You can do a search on
www.acvs.org for a board certified vet in your area. Good luck!