Still it would be fairly unlikely that a single tank would wipe out a platoon by landing accurate fire on every trench or foxhole, especially on flat ground.
Ground is rarely flat, tanks armament is couple of meters above the ground, and with 76mm HE rounds there is no need to hit right inside the trench. I am not even talking about firing HE with fuze set to delay action, where the rounds would detonate above the trench, after ricocheting from the ground. Even the US manuals (FM 17-12 Tank gunnery) of that period have that as a viable way of engaging targets.
By the way, machine guns were one of the usual targets for tanks of this period. It would be engaged either by the coax or with HE rounds. An MG in a prepared position is an extremely small target, yet they were successfully engaged in order to let friendly infantry move on. Sure, it will not be the first round hit, but bracketing is a perfectly good way to eventually achieve rounds on target.
There's also the question of detecting the presence of trenches on flat ground. If your vision is restricted to a tiny slit or periscope, or slit windows on the turret - the detection of those would not be immediate.
So there were absolutely no recon, aerial or any other kind? There is no signs of digging or clearing fields of fire? No parapets or they are perfectly hidden? What about binoculars? Commanders periscope sights, as those on a T-34? You are suggesting that a tank just happened by a lonely trench in a flat field? And the infantry is just sitting there without firing, no smoke or flashes?
I imagine if a trench system was detected HE shells would be fired by the tank for a while to suppress the trench. The infantry inside would cover and try to hold on to their dear life and hope that the isolated tank moves closer to them. When it does, platoon elements that are not suppressed and have AT equipment will engage the tank from close up.
So, he fires some HE shells to suppress the trench, and then for some weird reason he moves closer to the said trench, so that the infantry could engage it? He has great range and firepower advantage, why in the hell would he even consider giving it up? It would be even harder for him to engage the fleeting targets up close.
There is also a chance they will opt to hastily retreat either in an organized fashion or under panic.
If the player placed the trenches in such a fashion that the retreat is impossible (in the middle of a field, for example) than he can only blame himself. Behavior of the AI could be improved in this regard.
As for the tank, once it suppresses the trench it can either
a) wait for infantry to storm the trench - assuming there are some nearby
b) advance through the trench to use shock and try to collapse section of it - should be a very risky prospect for an isolated tank
c) ignore the trench and move on to a different objective
d) wait and observe from afar trying to engage infantry if they try to leave
I am not trying to argue about the tactics of this whole affair. There is a single tank and there is a trench. My opinion is that if a tank is aware of a large area target it is physically possible for him to land a few dozens good hits on it, damaging the defending platoon in the process. So a player should not expect to ambush a tank in the middle of a field, to achieve perfect cover once the infantry simply gets down, and should really try to support his infantry with the antitank guns and the like.
However what happens in game, is as described by OP:
you park a tank near a trench and then destroy the whole platoon one by one as they pop their heads out above the parapet for 3-4 seconds(too long). That is to my mind, wrong.
In these situations, 1-2 seconds is enough for infantry to assess what's going on. Also less of them would do so. In here because the timing seems to be generically set to the same interval for all situations(suppress stances) the tank can play whack-a-mole.
I partially agree with you on this. I have not played GTOS in a while (having fun with Steel Armor), but if i am not mistaken in the ambush mode there is significantly less of this whack-a-mole behavior. And infantry's role is to engage the soft targets that follow the tank. While they should stay down when the trench is being peppered with HE shells, they do need to pop up once in a while to acquire and engage the assaulting infantry, and it may be difficult to spot targets in 1-2 seconds.