I created an inanimate entity other entities may ride in my add-on, Phantom Frames. Skeleton riders do not honor the rotation value of the ridable entity and always face south.

I have tested all mobs and ONLY the skeletons will not face properly. Also mobs using a skeleton runtime will also only face south.

I can send images if this is unclear. I have not tested minecrafts rideable entities for the skeleton disparity, such as boats, minecarts, saddled pigs, horses, donkeys, mules, camels, etc... as it's beyond the scope of my project.

I just felt with the new ride rotation specs in the API, you should be aware.