Thanks for the update. I had missed that but now also found a thread for that from early January. (M142 P1 R35 S40 Gcode explained (X1C Chamber Fan Behavior)).
Maybe time to update after all…
Edit: I am still on older versions. When I need a higher chamber temp I just throw my cardie over the top, front and sides of the printer 
For stuff where I need actual chamber heat control, I have a Plus 4.