Imagine, if you will, a jam jar with a short thread. One of those French ones with the gingham top on it, for example. If you smash the jar, the lid will remain in place but the jar will be broken. If you undo the lid, the jar will be intact and the lid will be off.
Both states will permit the ingress of wasps when taking said jam on a pic-nic.
Now (and this is the bit where the analogy gets clever) because of the short thread it is possible to apply the lid without applying sufficient force to drive it hope as securely as one might like. This is especially easy in the case of rasberry jam, as the pips can rather clog up the threads.
Once the jar has been placed in ones hamper on the way to a pic-nic it is quite conceivable that the motion of the hamper may cause the lid of the jar to be sharply struck by an ill-secured corkscrew. Repeated strikes, such as those occasioned by driving over a cattle grid, may cause the lid to loosen to such a degree that upon opening the hamper at one's destination, one would exclaim "My word, that is not good! My jam, it is potentially exposed to the depredations of vespa vulgaris. That would quite ruin the planned pic-nic".
Happily, though, this dreadful situation can be remedied by re-applying the lid, as the jar is not broken. The wasp is thwarted and the pic-nic is saved.
Similarly the issues one might experience with a DMR Ex-Type crankset are easily remedied. As with the exposure of one's compote to insects, though, it is a fundamentally troubling design flaw. For this reason I myself prefer Tiptree prserves and SLX cranks.