This is a known issue.
My normal z homing speed is 6mm/s. Using P1 mode (analogue) it only reaches 2mm/s at the moment. I am putting up with it for now until @dc42 makes his changes. Like you I like the analogue mode as you don't need to fiddle with the crappy pots on the PP pcb as they are prone to falling apart if you keep adjusting them 🙂