Well, it is not a wives tale that BP's are finicky eaters and many times will not just switch back and forth from mice to rats... I have heard many success stories where people get a non-eating snake to begin eating on ASF, and later switch to regular rats.

Like everything with snakes, it takes time and patience. Some BP's will refuse till they die to eat rats... it's up to the keeper to be accepting and patient in those cases. Because sometimes, BP's just will not switch. Fortunately, I have never had to deal with that.

I have heard that it is easier to switch young BP's as opposed to older ones, and I also believe any seller should make sure that his snakes will take what ever is readily available before he sells the snake. ASF are still not that available, even here where I know there are breeders.

But again, I don't think your going to prove or disprove the rumor until ASF are readily available for everyone.