In 9.0, the Thunderfury appearances for the Dreadblades Artifact Weapon will sheathe on the sides instead of on the back like it is currently. I’m fairly certain that this is a bug, but the issue has persisted for each and every PTR build.
And yes, I have been sending bug reports in-game on the PTR on nearly every build they have put out.
I really hope that they fix this because the fact that the Dreadblades Thunderfury appearances sheathe on the back is one of the most appealing aspects of these sword appearances IMHO.