To clarify this, the Axe-Fx III has no audible gap when changing channels on the Amp or anything else.
For the record, totally switching an amp — on any modeler — requires a brief fade-out of the old sound, followed by an equally brief fade-in of the new sound. Without that, you’d hear a nasty CRACK! In your speakers. For years, I thought my Roland GP-100 had gapless switching, because I couldn’t hear a gap. Only when I analyzed it did I realize that there was a short gap of less than 50 milliseconds. Too short to hear.
The Axe III beats that performance. One beta tester measured it at 37 milliseconds. It just feels and sounds completely seamless.