Shield-crush does happen, but in most cases what people are experiencing here, doesn't have to do with the feature. Nine times out of ten, it's any one of these happening:
(1) enemy attacks connecting at exposed parts of the body
(2) late block timing
(1) most often happens when playing in third-person, because the pseudo-isometric camera is not precise. What people think to have been a proper block, when seen in the first-person, often turn out to be flawed. Difference in relative positioning very frequently exposes your shoulders, particularly when the shield is narrow and vertical -- Imperial kite shields are particularly prone to this problem. The most frequent instances by far, is when using such a narrow shield against an enemy with pretty high athletics.
Enemies with high athletics on higher AI setting actively add lateral movement to hit your exposed spots... if you're blocking left they aim for your exposed right shoulder with horizontal strikes, if you're blocking right, they move to your left and target the left exposed shoulder with horizontal strikes. And then, at some point they mix in a vertical slash -- and when you hold your shield at high position to block this, there's a very likely chance a misalignment happens and your right shoulder is exposed.
Imagine yourself holding a narrow shield at a high angle -- the shield doesn't cover your exact middle point. It's a bit slouched to the left, because the shield is on your left hand. In this situation, if the enemy is misaligned a little bit to your right side (around your 1~2 o'clock position), then his/her vertical slash will travels down the right side of your raised shield and connect on your head or right shoulder top. This is very clearly observable in first person, but in third person, it can look deceiving, looking as if the hit just passes the shield and hits the head/shoulder.
Another good example is when fighting against spears. Unlike swords, spears can be aimed very low toward the feet, or very high toward the forehead. When you see this attack in first person, you have to go in low block and angle your shield pretty low to guard your feet, or angle your shield higher to protect the head. Exposes points will be hit. But when you see this attack in the third person angle, all you see is either a high thrust or low thrust, without precise info on actually how low or high the attack is aimed. This often causes confusion that "the attack went through the shield."
(2) happens when people fail in "parry blocks" (the timed blocks that give out the different block sound effect and allows for quicker riposte). When the timing is really close, it looks like the hit goes through the shield, but what actually happened is your shield-block animation plays almost simultaneously to the enemy attack landing on you. The attack did land before the block, but the margin is very small and it causes confusion.
In over 210 hours of play, I've never received a hit I cannot understand or explain. I've never had a "attack goes through my block" issue, and I think it's because I've exclusively played the game in first-person in almost all combat situations (except for quick check of the surroundings).
