I think people throwing around polish power are low key just trying to get away with saying White Power.
Lurker for many years here, I've signed up just to answer this
. On the one hand I don't completely disagree, but Jan's not saying this, he's saying "Legendary Polish Power", as if it was some sort of a magical trait from AD&D, and as such I don't think it has those white power connotations.
More generally my take on this is this: he needs some marketing power, obviously while he does come across as a nice guy when he speaks English, his English is a bit basic and broken at times. So if he wants to be sellable, he'd need to either radically change his personality and improve English to become more of a smug trash talker, or try something else. And you know what, I don't think marketing yourself as the Possessor of Legendary Polish Power is the worst thing he could do; maybe with that his imperfect English is actually "on brand"!
I can sort of see how, in case he does beat Izzy and maybe Glover afterwards, UFC uses this slogan big time for a big Blachowicz-Jones fight (many ifs here I know), and casuals actually do get interested/intrigued/whatever and buy ppvs big time. After all, this is the era of Game of Thrones, Hunger Games, and other big fantasy stories, and UFC is an "entertainement first" enterprise. So I really think it could work as a marketing trick, and the slogan "Legendary Polish Power", as used by Jan, should only be viewed in this context imho.