The thing with ostheer is that you generally use smoke to close distance and ostheer performs best at long range
You won't be performing at all if you get suppressed by an HMG team though. I would disagree that smoke is used more often to close distance than to avoid getting pinned down.
@OP: Any kind of smoke is incredibly useful, both in attack and defence. Even if your opponent knows how to use attack ground, the appearance of smoke can still cost them some seconds before they switch to using attack ground and manually tracking their target. Also, attack ground produces more misses than normal attack mode when stationary.
It can also be the decisive factor against long-range TDs like Firefly/Jackson/Su-85 in disrupting their LoS at the same time as using blitz ability on your vehicles to close distance and flank.