It's more about being in position to block. I understand the one knee advocates think it allows the C to get in better position to receive at the bottom of the zone and "push" the mitt up on receipt. Pitchers in this league have it drilled into their heads to miss down (as missing up leads to 400' deposits), but it can absolutely be done without going straight to a knee. As we saw in the top of the eighth last night, with a runner on third, it's a 50/50 proposition that the C can get to a ball in the dirt properly from that position. It just shouldn't be tolerated, much less promoted.
Check out the Arkansas C (Optiz), and notice the "hop" into outstanding position with runners on base which our guys DO NOT DO.
This is how it should be done....