Colour changing gaiwan question

I bought a “magic” gaiwan, one of the ones that has a bare tree branch on it that shows flowers when the temperature changes. The listing said it changes with *hot* water, which would make sense for something you brew tea with, but the one I got shows the flowers when it’s *cold*.

I’m assuming it’s an error, but is there anything you could actually brew in a gaiwan with cold water?