Betta Fish: Is this a deformity?

1st pic: a month ago August 1
2nd pic: today September 1

I save bettas I find most vulnerable in pet stores. This is my most recent betta Ive bought, got this stressed guy because his colors were faded and mainly his tail shape caught my eye. I put a sort of drip filter in his tank due to his tail and long fins. Thankfully now his colors are popping but his tail shape didn’t change.

I’ve never seen a betta tail shaped this way. Is that a deformity on his tail?

He was a “special buy” from PetSmart so I’m not sure what breed he is.