It seems like, if it does not matter, if you check the box or not. Bambu Studio always calculates the speed of overhangs like it is checked.
Using expanding filaments like PLA Aero causes problems when using different printing speeds. Extreme slow-downs give the filament time to ooze out of the nozzle, causing to less pressure inside the nozzle. This results in extreme under extrusion.
Bypass: set all speeds to the same speed you want to print anyway.