Yes, the output devices are Gallium Nitride transistors. Much higher efficiency and higher rise time than silicon for output devices. Switching frequency increases over silicon. The latest Class D amps with Silicon MOSFET outputs switch at around ~500KHz. The GaN output stage in the BOSC switches at ~750KHz. This makes filtering out the HF output easier with better quality components. Other parasitic types of problems are lower on GaN devices, so simpler drive circuitry is part of the design.
Note: Leo may still have his Starkrimson)old BOSC GaN amp) monoblocks available for demo.