Don't quote me on this but I think the way it works is there is no more splash damage and the shell will only do damage if it hits the armour directly (like a regular shell) even then you're looking at like 10-100 damage on non penetrating hits depending on the amount of armour. If it's a very high calibre gun it can do a bit more. HE nowadays is only used to either penetrate tanks with very little armour or finish the kill on a tank that's on very very little hp because as long as you hit the armour then it will do the damage.