Wanted to provide an update on this issue as I have recently revisited it and its still present.
This is using the latest version of XParticles and V4.03 of Octane.
It seems to be related to the Z axis. In the this screenshot you can see my animation of smoke trails following some missiles, this is animated along the Z axis using an attractor. However in the Octane viewer you'll notice the exported VDB being rendered completely mirrored to the actual animation.
In screenshot 2 I have rotated the attractor around to the X axis and rebuilt the cache, this animation seems to render fine in the Octane VDB object, following the same path/size as the previewed ExplosiaFX on the left.
So it seems to be related to Z axis data, I don't know if Xparticles isn't exporting it correctly or if the Octane VDB volume is not understanding it correctly. For this animation I can rotate everything to animate down the X axis but for things that spin in all axis this isn't going to help and a fix is needed,
Hopefully this info is useful in getting it fixed as Id love to have it work properly.