Even if you take that website at face value, the ELO scores shown are relative to the other AI models tested, and not comparable to the ELO scores of humans who play against other humans.
As a 1500 elo human I can tell you that a 1500 elo chess engine doesn't play like anything like a 1500 elo human.
Conservatively there are well over 10 to the 30 positions likely to show up in realistic games.
There are of the order of 10 to the 10 or so games recorded.
Thus well under one in a trillion positions are "known".
Edit: maybe you don't understand what i mean by novel position. I mean any position that has never been reached in the billions of lichess games, including bullet games among beginners.
Also yes I will concede that it's possible to make "quiet" moves. pawn nudges that barely affect anything. If you're doing those you're not 1500 ELO. You're intentionally trying to throw wrenches and I just don't see why an ELO bot even needs to bother with nonsense like that. This is supposed to be for fun / training!
I am around 1500 (actually 1649 on lichess blitz, but close enough).
I explored the last 5 games I played on lichess. Here are the number of moves before lichess had never seen that position before for each of the 5 games: 6, 12, 16, 15, 11.
> If you find yourself in a novel position within 10-15 moves it's likely a resignable one
The opponent is also going to be in a novel position. Should both players resign?
Just in case you think this is limited to low rated players like 1500s, look at MagnusCarlsen's most used account on Blitz: https://lichess.org/@/DrNykterstein/search?perf=2
You will see that most games become unique to the whole of lichess within 15-20 moves and a good chunk between 10-15.