MIDI Remote API vs MMC - MMC comms not working

Hello. Already posted this as part of another topic but that went off to address my second question, resolved, so re-posting here to keep it simpler.

I have a virtual MIDI IN and MIDI OUT port that use MIDI messages to perform a variety of tasks, in Cubase and/or on the other end of the bidirectional link (mostly visual on the other end but some cause messages to be sent back to Cubase). Works well, and is happily talking to the software I’ve written for this purpose with Generic Remote. What I can’t then do with MIDI Remote (after removing the Generic Remote mappings) is use the same ports for MMC - the MMC messages are sent to Cubase, e.g. “Get current position” but no response is sent from Cubase. Yes, I could create some more virtual ports for this, and doing so works, but that seems like a flaw in MIDI Remote.

Any ideas?