I agree that looks more like damaged fins healing, not crowntail genetics. I notice you have a blue plastic plant in his tank, those can damage betta fins. You should get all silk fake plants instead, also grab a cheap nylon stocking
at your local grocery store (usually near cosmetics or meds-that's where I see thenyways) r dollar store and rub it over EVERYTHING under water that is not a live plant (fake plants, any decor, any part of filter under water). If the nylon snags or tears that item will damage betta fins and should be removed/covered/adapted. Depending on what the item if it may be safe to sand/soften rough edges but some resin decor items are coated to make them "aquarium safe" and sanding removes the coating making them not safe to put back in the tank as paint chips will get loose.
you are using an HOB (hang on back) filter you need me make sure the intake has a cover. You can buy a cheap small piece of filter sponge/foam at the pet store and cut a slit (with scissors or carefully with a knife or razor) in it to slip over the filter intake like a very thick sock covering the holes completely. This lets water continue to pass through easy and make it betta fin safe, it also has the added benefit of becoming an extra are for beneficial bacteria to grow. However the foam will reduce flow over time as it gets clogged with mulm (broken down organics). So periodically taking it off during a water change and squeezing it in the water change bucket/cup is a good idea.. frequency varies depending on your tank stock (snails make a lot of poop and mean the filter cover will need cleaned out more often then is there is only a betta in the tank).
Just some tips to help the fins heal and stay healed ^^