Why doesn't Airbus modify the standard call to 'flaps 3' for a Go Around ?.. That way, there's no ambiguity and no excuse for not knowing what the go-around flap position should be.
Exactly.
In a Boeing go-around, the required flap setting is called for (varies for single- and 2-engined go-arounds, according to the model).
As Jeremy Clarkson would say "Why can't they just get it right?"