You are ascribing motives to the OpenZFS project that aren't there. Sun was the one that licensed it CDDL, and OpenZFS is a fork that was created when Oracle bought Sun and decided to close source ZFS. Oracle has zero involvement with OpenZFS.

Since the pre-fork code is from Sun, Oracle owns the copyright, and they won't re-license it.

The idea that the OpenZFS team wants CDDL out of spite for Linux is an absurd conspiracy theory. Their hands are tied - I'm sure they'd move to a compatible license if they could, but they can't.