Great guess! Midihub does give real time data more priority, as suggested by the MIDI 1.0 specification:
To help ensure accurate timing, System Real Time messages are given priority over other messages, and these single-byte messages may occur anywhere in the data stream (a Real Time message may appear between the status byte and data byte of some other MIDI message).
We’ll add a flag to Transform pipes to allow disabling the higher priority of the produced real time messages, and another flag for controlling whether the generated message should go before or after the original event. This will allow you to achieve what you’re after.