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"the infamous johto level curve"
google search results show a single mention of the term, "johto level curve" between January 1 1999 and Jan 1 2007. Clicking it turns out to be a GameFAQs thread posted this year that seems to be an anomaly in terms of why Google is backdating it.
This was a term invented by Youtube video essays grasping at straws to come up with "objective criticisms" of a game. GS as the best games in the series was settled science until a bunch of peabrains came along with their "hot takes" and "ok boomer" bullshit