People are more familar with Abloy style disc locks now, but its a type of lock that is still not encountered in the US often. People expect that a correct key will turn the lock more than a trivial amount, and the wrong key will not budge the lock any degrees. However with detainer disc locks, they will always turn 90 degrees regardless if the key is right or not. Abloy has mitigated this problem with newer lock designs (the Exec and the Protec have this) with a disc steerer mechanism that won't allow the lock to turn unless the key is completely inserted. However, bike lock cylinders are still in the Stone Age, so people insert keys part way, the lock won't turn past 90 degrees, and they are not used to aligning all the detainer discs.
This isn't to say that some locks don't break. I've heard of cases where even used correctly, some cheaply made bike locks will have trouble and break at the cylinder linkage (where the cylinder turns, but won't unlock). To prevent this, go with a known good brand that has been around a long while.