Earlier quoted context omitted.
From comments and personal experience, it is incredibly likely Elon screwed up the rollout and the "600 posts/day" isn't accurate and is triggering much, much sooner than expected.
I think a ton of users will hit 600 "posts read" really quickly, if that's what they're measuring. Refresh your timeline, load 20 new tweets. Tap a tweet, load 10 replies, etc.
This is not semantics, as tweet impressions are a separate metric Twitter tracks and would more intuitively represent reads.
Unless Twitter engineering did some malicious compliance for Elon.