I've heard this before, but I've fed quail to my rtb and sstp, didn't really notice any difference. Maybe if you feed only birds? I offer mostly rats but have given guinea pig and quail before, I've got a couple piglets in the freezer I'm going to try on my bigger snakes one of these weeks too.
My experience has been that live chicken has nasty results. FT chicken/quail does not. Never tried live quail.