Yes, that is how it *should* works I suppose. Again I do not have UE, but exporting with UE settings adds UE IK resulting root bone movement by X when importing back to 3DX > iClone and adding a lot of jitter by X in a way.
There are a lot of UE pros who should be able to help with importing UE motions and exporting it back. Anyone?

77% of original size (was 653x19) - Click to enlarge

Ok, thank you so much for verifying. That really helps me.

I would say no, this is not a desired behavior - as it also creates the exact same jittery animation inside UE. It is possible I may have stumbled onto a bug. There are situations where you might want the root to follow the hip, but not in every case - and I suspect the 'turn if off' button under the advanced panel is not working and is always exporting as ON, locking the root to the hip no matter the setting. I'm chatting with support, hopefully they have a fix/solution. Again, thanks for helping me with this - knowing it is just not me is a relief.

As an aside, do you see any jitter in feet that have been locked by a reach effector and exported as FBX? I have tried baking the effectors in the Edit Motion Layers panel as well as not baking them - and while in IClone the feet are rock-solid, in any exported FBX (including Blender) there is still a very slight jitter to them. Nothing as bad as the first issue I was talking about, but definitely noticeable.

As an aside, do you see anyany jitter in feet that have been locked by a reach effector and exported as FBX?

Definitely, Baking Constraints is not exactly a perfect routine either. This is true for exporting to FBX, or saving as Motion+. You only get almost 100% with Reach Effectors inside iClone.

Thanks again for verifying what I'm seeing. I really love working in IClone, so I hope they put some focus on cleaning up the exports as little. Anyhow, thanks for walking with me down this windy road, I def appreciate it.