He was pretty cautious in the WN, and for good reasons : it's a more realistic world than a lot of fulfilling isekai out there.
He isn't arrogant and doesn't tell them for the fun of it, he doesn't tell them because how the fuck should he explains that knowledge ? "So I was playing a game, then got reincarnated in that game world, can change jobs, have an OP sword, can use magic and oh yeah other people have levels and I can see them. How do I know that ? Welp I'm the chosen one".
If I was in his place, I would be more secretive and cautious, he could be killed for that amount of information. So I don't really understand the comments on that...