You can take any kind of wood out there, and I bet you can find a turner that doesn't like working it.
Sure are a lot of walnut gun stocks out there for the wood to move much. Know what I mean?
I'm thinking you got fibbed to a little by someone that turned a peice of walnut that was a little wet.
With that said, it is always good practice to let a pot call relax after turning it, and again after finishing it prior to surfacing it. There's all kinds of new pushes and pulls on a pot compared to what it was in the blank, or even board form. I do this, because I want my pots to last for a long, long time. Do you HAVE to do it? No. Am I doing it to help save ONE call out of how ever many I ever make? Yep. One is enough for me. I am in no rush.
Parker