If you test sending a 3 byte message such as a Note On/Off or CC to Midihub and receiving it back over DIN-5 MIDI, the latency is around 1.92ms which is consistent with what you would expect such messages to take traveling back and forth over DIN-5 MIDI cables at the rate of 3125 bytes per second.
Sending and receiving 3 byte messages over USB MIDI it’s around 0.96ms.
The time taken by Midihub’s processing is insignificant compared to the time it takes for the messages to travel via their transports.