Point one, this is an old (ish) Flight simulator. Point two, this is not the hyper realistic DCS. Point three, there has to be some poetic/artistic licences taken, as this is a simulator, not real life, the guns in game however, are good, yes maybe your example is on the more extreme end of the scale, also I am not sure of the hitbox/damage box on the A-10 modelled in game, so it is possible that it is down to the damage model of this particular aircraft. Were the rounds incoming from the ground, or from the rear ( engaged by a bogey) Finally, A 30mm round with depleted uranium, will reach out and lovingly caress anything ( within reason) that it wants to, as mentioned above ...............
I would agree that armour in some cases is relatively easy in some cases, however, I redirect you to my previous 3 points, rinse and repeat.