Does enabling accurate motion vectors fix blurring for all WPO math? I’ve found that it fixes the blurring for speedtree assets (presumably because its wind effect is done through its own WPO node) but not for objects using custom WPO math. Are there operations I should avoid doing inside there? 
I have noticed the same thing. Speedtrees are pretty sharp but custom WPO isn’t as sharp.
It’s only fixes time based movement.
Its now entered as UE-24905.
I’m pretty sure all foliage WPO anims are driven by time?
It is probably the most common use case, but there are other ways. For example you can also drive animation with a parameter that is updated every frame.
I’ve got a case where I am using imposter sprites as ground foliage. they exhibit temporalAA ghosting to. I’m guessing because the effect isn’'t time based world position offset? I didn’t know about the accurate motion vectors project setting. I’ll see if that helps.