It was hard to tell, but I think I saw the piezo switch on the P24 in the middle position. That would let you mix piezo and humbuckers, and I wonder what the mix was?
Can't wait to try this on my P22!
The producer and artist address the piezo in the comments below the video, no piezo was used for the acoustic simulation. The artist says in the comments that the piezo doesn't mix well with the simulation.