Nevertheless, I agree with you. It's much easier to use the sector MEF figures and add 1000' to get the MSA if you're using the 1/2 mill CAA charts.
Yes, and only if you don't like the answer do you bother with the more detailed examination of the map. Which you might do if, for example, the MEF is obviously due to a tall mast in the far corner of the square, nowhere near where you're going, and the MSA calculated on the MEF is higher than the base of CAS along your track.
But of course such real life discussions have only a little to do with guessing which is the right answer in a multiple choice exam ...