Jen says to him, "If you play the game and you lose..." and he interrupts her (for the second time) and says, "Say no more!" Later, she says his mistake was never asking if he could opt not to play, and she points out how crazy it was to interrupt her instead of hearing her out.
I'm assuming the instruction was going to be, "If you play the game and you lose, you and your friends will go to the bad place," and if he had more self-insight and self-control he should have said, "Wait. This is my favorite game, but if I have to play against the Jaguars, there's a real chance I might not win. I don't want to put my friends at risk. What if I don't play?"
I'm undecided whether I think that was unfairly testing his intelligence as well as his selfish impulsivity. On the one hand, Eleanor probably would have figured out the catch just because she's smarter. On the other hand, we don't know if Jen would have dropped more hints for him if he'd let her finish.
And I agree that the point of the show is that this is not a just way to judge people eternally, because people can grow and change. Jason has improved, just not enough. But if he could improve given more time, it's not right to torture him forever instead of giving him the chance to keep learning. I don't think we were ever supposed to think the current system is right.