Way too many snakes to keep birth and feeding records on but not so many he knows the one you are about to buy is feeding well?
Sounds fishy.
I'm not sure I see the point in contacting a breeder who has so many snakes he can't track them but all, but conveniently knows the one you are about to buy is a good feeder.
Good luck with her. Odds are she'll be fine and eat for you, so if you like her that's all that matters.