Does your dog have skin problems? Is anyone in your house allergic to dogs?
The shampoo is soapless and is probably fine but I agree with you on why he wants you to wait to shampoo and also why buy it on the 1st visit. My guess is that he makes $$$ on the shampoo.
I would also guess he does not want you using cheap dog shampoo's because they will dry a Yorkies coat out. Many members use CC products and I use Coathandlers.
http://www.petcarerx.com/affiliate_p...pdp=2&upsd=699