My wife's animal hospital employs one of the top Herp specialist in our province, and she too also recommended Soy yogurt as a probiotic while I was treating my little girl for pin worms.
Are you sure you said "SOY yogurt"? and not just "yogurt"?
also the doc said that soy yogurt is bad, because the good bacteria for mamals, can cause disease for reptiles, so just wanted to put that out there, and this woman knew what she was talking about trust me 1 hour visit
Soy is made from soybeans so it has nothing to do with mammals. Are you sure you didn't just mention yogurt and the vet mentioned that reptiles can't digest dairy? That's why we use soy instead.