where does the idea that "better jungler wins" come from?

???

I've been part of wayyyy too many games where the better jungler loses, both junglers are doing amazing, or both junglers are irreverent. It is SO common for one lane to absolutely get shit on then have their opponent just be a terror to the rest of the game.

I've seen Fioras dominate games I've seen Zeds and other mids dominate games I've seen every adc you can imagine dominate a game

Sometimes the better jungler wins, but i don't see it anymore, or much more, than any other lane