Ah good old equivalence rabbit hole
F2.8 is f2.8 as far as exposure is concerned but for DoF field it's equivalent to f5.6 on FF.
But that's not the end of it... A FF sensor is capable of gathering 4x more light than m43 sensor. This gives it better performance especially in low light. So basically a FF sensor is about 2 stops better performance than a m43 sensor.
So what that means is one could get the same performance i.e. image quality out of a FF sensor by sticking a f5.6 lens on it as they would out of a m43 sensor by sticking f2.8 lens on it, all else being equal.
To compare like of like i.e. similar/same performance you'll need compare m43+12-40/2.8 with FF+24-80/5.6. Using a faster lens on FF would give it an advantage over m43 (possibly at cost of physical size)
Such a lens doesn't exist on FF as far as I know but I am not talking any specifics here, just plain old equivalence discussion