First, the issue is that he's winning at a rate that is 10+ standard deviations above what the typical winning/profitable player is achieving. These results are accomplished across a significant sample of sessions (39 live streamed ones), and across almost a year.
If you consider some of the players considered the best "live readers" in the history of the game (Ivey, Negreanu, etc.), none have won at the rate that he has.
Secondly, he's playing $1/3 and $5/5 poker in a city (Sacramento) that is not exactly a gambling mecca. You would expect someone who is as good as he is to play higher stakes games. $1/3 and $5/5 are stakes offered at nearly any casino.
Third, he's performed well against some elite pros. Matt Berkey (who regularly plays the highest stakes in Vegas) was in a streamed game against Postle, and Postle performed extremely well in heads-up hands. Given that Berkey is playing for hundreds of thousands of dollars on a nightly basis in Vegas, and seems to be a profitable player in those games, are we supposed to believe that Postle somehow has identified body language tells that no one else has discovered?
This is not even considering other facts like:
* Postle used to consult for the production team behind the streaming for the casino
* Postle used to claim to run some kind of app development company, and has since deleted his LinkedIn
* The extreme winning sessions seem to only have taken place during streamed games
Sure, it's possible that there's a benign explanation here, but it's looking far and far more unlikely.