I'd have to see him flare. Sometimes PK's can actually get a point to their tails, it's kind of a throwback to wild type Betta's who often have those points to their tails. Plakat's were derived from Wild's and then long finned out from there with hybrid breeding. Anyway, if you put him next to another Betta, they should flare (please don't put him in the same tank without a divider though! lol) and you should be able to get a nice view of his tail!
But one cannot really tell the Betta's genetics just by looking at their fins, you'd have to contact the breeder for that but that's really hard when they're from big chain stores lol but no worries, I'm sure he's still full of energy and will be right as rain once he gets into warm water and get's that belly full of food!