the d/g button accordion is not fully chromatic.
you do not have an F natural,g# a# d#,you cant play fac f major chord,b flat d f, b flat chord,eg#b, e major chord,g#c d# g#major chord,c#fg# c#major chord.f#major chord f#a#c#.thats alot of chords you cant play.
you can of course play a and c,which fits the F major chord,but could also be part of an A MINOR CHORDbut sometimes you need that f root.
DickMiles