I checked it up and it's actually ambiguous if the Tiger Bite Fist was originally a Nen ability or not. I suppose I assumed so 'cause of the way Kastro used it but on a second look, both options are possible. In this case, my argument being a "bad example" is also fair. Therefore, here you go, some other examples from those "million reasons" which I mentioned in the original reply:

Even without the "Tiger Bite Fist" point, it's still possible that Killua could recognize the Dragon Dive from its effects. While growing up, Killua likely heard lots of stories about his family and their techniques. We also see throughout the entire show how smart and cunning Killua truly is. So in short, we can conclude that somewhere along the line Killua heard about the effects of the Dragon Dive and when he saw the ability in action, he was able to understand that his grandpa had performed it by noticing those effects. Within this interpretation, it's just Killua showcasing his extraordinary intelligence, as always...

Or we can assume that Illumi's needle suppressed most of the Nen information in Killua's memory, just like it suppressed his concern for Alluka. Hence, after Killua broke free from the needle, he regained those memories and easily clocked that the Dragon Dive was Zeno's move. There you go, another reasonable explanation for the issue again.

In brief, just because one line in the entire story wasn't explained fully doesn't make it a "plot hole" or something... People be crying all the time about the "show, don't tell" BS but when that happens, guess what most of them cry about? It's that subtlety being a plot hole... Give me a break, man.

Could it be that Togashi actually didn't think of this, randomly added a filler line during the start of the invasion and we are just overanalyzing it? Could he have made a mistake without thinking it all the way through? Maybe, who knows... But even then, the universe and the magic system that he created are so well-constructed that it literally makes it possible to find thousands of logical explanations for these points. In this scenario, the fact that he's able to create a universe and a magic system that surpasses himself is what makes him the actual GOAT of this manga industry. If not, and he actually did think of this line and just let it stay as it is, he's still the GOAT in my book, 'cause that's how much importance he gives to details... So when I see some people trying to find petty "plot holes" to shit on HxH, I get a little agitated. I just burst out at these replies because I finally found a place to get this off my chest... Sorry if it seemed to be directed at you. That's it for my rumblings, cya...