[_heimdall]

How would one detect it?

As far as I'm aware, you would have to know the full list of cards in the shuffled deck before the hand was played to know they didn't change the community cards.

[sejje]

Because it shows up in analysis of millions of hands.

The community cards are subject to the same frequencies as the hole cards.

(And you can see them more often, so they're actually easier to analyze)