boiling water containers doesn't change the description of the water container

[alchemist]

a leather wineskin remains a leather wineskin, after boiling.

Why not 'a boiling leather wineskin'?

[brazen]

Because the wineskin isn't boiling, the liquid inside is! (badum-psssh)

The difference here is the wineskin is re-usable, the liquid inside is what actually gets altered. You can still pour out the contents, so changing the long description of the container involves a lot of sanity checking.