The fact that you're better at blitz than someone does mean you're better at longer games but I always find accounts like that suspicious. The other day I played a guy rated 2000+ rapid and under 1400 blitz. I absolutely crushed him. There's no way that guy was a legit 2000. Either that account is used by multiple people or he's a part time cheater and I just got lucky and got one of his honest games. Maybe something similar is going on with this guy too.
How is this possible???

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https://www.chess.com/article/view/chess-com-fair-play-and-cheat-detection
https://support.chess.com/customer/en/portal/articles/1444879-fair-play-on-chess-com-what-you-need-to-know
The guy I just played is X. Rapid and X blitz:
[removed; public accusations or implications of cheating not allowed; also removed the ratings -- VP]
and he gave me a good game in rapid before he blundered. I am 1900 blitz, so I should have crushed him?!