[Renton]

because when you calculate ranges and the overall game into things, his bet has a entirely different ev attached to it than his call of our bet of the same size.

If we bet, he calls, he payed to see the river, and unless he's running some elaborate turn-float-river-bluff, he's essentially depending on showing down the best hand as his only way to win.

If we check, and he bets, and we only call, he's essentially making a winning play against our range, because

a) his bet has folding equity (i.e. he can win the pot in TWO ways now, by making the best hand or by making us fold)

b) he gets a free card if he's drawing against us

c) he gets to cheaply show down, since the dynamic in the hand has changed to a mode where you are going to continue to play passively and check the river to him, giving him the option to take a showdown.