The filament properties belongs somehow tied to the extruder instead of the process.
If you load a duel extruder profile you can't set different filament properties (mainly diameter although cost is a nice to have too) for the different filaments. So basically you have to change the multiplier for the extruder beyond what you'd normally have to if one of your filament has a different diameter. Sort of annoying if you have multiple processes that use different filament diameters for different filaments but then you want to make a process that uses both extruders... now you have to recalibrate instead of just copying the numbers.