Fwiw, I recently did some experiments using the MIDI ports on my RME Hammerfall Multiface units - looking at audio recorded back from my Elektron units.
Timing via those is surprisingly impressive. I’m seeing negligible drift.
I’m not sure that a sync-gen type unit could improve on it much.
Those are connected via the PCI-E bus though. I’ve not had such good results with USB based MIDI devices.