With a very thick glass, you definitely can crack it with boiling water. I didn't know if earthenware is similarly susceptible, but anything that is both brittle, and has a high enough rate of thermal expansion would be.
Sure, thermal expansion can crack ceramic. More my question is, did this really happen? The operating parameters for a ceramic cup are well known. A cup that is ok for 90C tea vs 100C tea seems like terrible design which would run you out of business if your competitor could make cups that were not known for breaking if you did not let the water cool long enough.