Im using an Arturia Beatstep- But I am under the impression It can’t do it because I only attach a single MIDI cable. 

Does yours do this? Catchup? Or does it just pickup the absolute position right when you start to turn the knob?

You are right : how to catch up a pot if you don’t know its position from H9 ?

The Catchup feature is handled by Timefactor but not H9.

I use absolute position but if one day H9 will be update to do Catchup it will works as Catchup if option is enabled.