Every serious sniper knows the curve doesn't exist and a missed shot is on the shooter/spotter, not because of the curve/spin of the Earth.
I should of added - but they know it only effects a incredibly small number of shots.
So we agree to a certain extent. Blaming the spotter? Only if the DOPE is incorrect.
Coriolis Effect? I can tell already that that would be a long discussion with you. I can say that I have seen it effect shots depending on the angle the shot is taken in relation to the rotation of the Earth.