Procreate crushes the battery, as you’d expect it to do, with dozens of Bluetooth handoffs every minute of drawing. Granted, I’ve used my iPad Pro a lot over the last year, (including resource hogs like Shapr3D) so the battery may have degraded a bit.I had the 2020 12.9" iPad Pro, and used Procreate a lot. I never had that kind of battery drain.
Also the GBP uses Wacom EMR for the pen, not Bluetooth, so it’s far less demanding on the processor for drawing. For other tasks, my GBP and iPad Pro get similar (and very impressive) battery life.