That's right. W^X is a policy that memory is either writable or executable, but not both. OpenBSD uses this model in userspace, now it's being taken a step further and applied to kernel space.
I assume the policy is W nand X rather than W xor X. First I've heard the term, so I'm risking pedantry to make completely sure.
According to [1] it's W xor X. Interpreting that literally suggests that read only memory is disallowed as well. I'd be surprised if that's actually the case.