No Turret - Defensive fire clearification

[greo]

In the "No Turret - Defensive fire" thread Y2Ask answers in a question where the example is "A PzIV moves in a hex that contains a SU". Isn't that move dissalowed by the rules anyway? Only 1 of 4 units can be a vehicle in a hex, wright?

[Y2UAsk]

The PzIV can't stop in the hex with the SU, but it can move through.

Steve