"Everyone knows the saying that ‘time flies when you’re having fun. But the full story might be nuanced: Time flies when you’re having more fun than you expecte

"Everyone knows the saying that ‘time flies when you’re having fun. But the full story might be nuanced: Time flies when you’re having more fun than you expected." Is it such a new concept? I mean if I am just enjoying playing a game, sure I am not so engrossed in the process and might be thrown out of the mood and focus elsewhere. Time does not really appear to be "flying". I understand the common feelings too have to be checked by science, but if it rings true already, is it a big revealation?