Yeah, I do think that's splitting hairs. A large part of that is what being good at the game actually entails. Also, you're underselling it -- it's not memorizing specific ways to die per se, it's learning a large number of different strategies to deal with a large number of different problematic situations. If it were just simple memorization the programs would be better at playing it. Ironically, the vibrating square is one thing that a program would do much better at than a person (also Sokoban) -- it's mind-numbingly boring for a person to do, and you can easily mess it up and frustrate yourself to no end, but a program will execute a perfect sweep to find it in no time at all.

A large part of becoming good at NetHack ends up being learning to be patient, playing conservatively, and taking lots of time to think before acting. And there are plenty of mini-games within the game (such as Sokoban, potion/scroll IDing, pudding farming setup) that you need to learn well too.

What helps most of all is being resourceful. There are so many different systems in the game that can all be used in the right situations to give you an advantage (e.g. Elbereth, wielding cockatrice corpses), so you just need to play slowly and cautiously and continuously think about every single possible action of the dozens available at any one point that you can use to maximal effect in any specific hairy situation.