Some stores do get them from USA mass bred places. Because it is cheaper, then to import from thailand. Not all stores get them from thailand. I know this about stores in MY area.
To be honest however, it is up to YOU what to breed. My doubletail does have the "mitten tail" as mentioned above, but it is not as noticeable. The cool thing about bettas is that you find another, to offset the "bad" in a fish and create something wonderful. How else would half-moons, doubletails, etc exist? Magically? Unlikely! It took time, effort, and someone who wanted perfection to create such finnage.
Although I will say I do notice the uneven head, which can be like spoonheads where some of the fry may or may not get it. You just never know... Personally I wouldn't breed him for that reason, but again it is up to you :)
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.