You're referring to the time it takes to do program changes. The actual timing of playing the notes on the PLG boards is quite fast and has even been improved over the S80 and CS6X.

The main reason that it takes a little longer is that the Boards are just like separate tone modules and Motif is sending more than just a simple Program Change. Motif sends a regular program change message and then all the offset parameters that are contained in a Motif PLG voice.

These include the 32 Native parameters that you can edit and store on Motif as a PLG Voice. So these take longer transmit than a simple program change. However it really increases the flexibility of the boards to be able to edit those parameters directly from Motif and store them in a Motif PLG Voice