What? W^X implies that Write and Execute or mutually exclusive, can't have both active at the same time.
> They "invented" that, what 5-10 years after Linux?
It's not so much that they "invented" it, but that they're much more diligent about making sure all the base system and ports use it. It's enforced that unless your file-system is mounted with "wxallowed" then any process that tries to mark a page both writeable and executable will fail.