I think your analogy to a crease is not unreasonable, but depending on the severity of the crack my tendency would be to give them a lower condition than I might with a crack. Those cracks can really detract from the overall appearance of the cards. A surface crease on a regular card doesn't impact the appearance as much as a crack. A full crease that goes all the way through is bad - like a crack. Other than the cracks, they are fairly sturdy cards and it's relatively easy to find them with sharp corners and very little signs of wear.
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