Ideally camo would only work if stopped, as OP noted should have put up/take down time of at least a couple of minutes. Getting strafed at that point could/should kill your crew, leaving you a tank with no one to drive.
Once camo'd it should ideally remove the icon entirely, or lower it. Giving the tank a better chance to stay alive.
As to digging in, why do you think soldiers dig foxholes?
It doesn't help them charge or attack at all.
But it does help keep them alive, especially when getting hit by Artillery.
Same for digging a tank in, protects the vulnerable area's, especially by artillery.