Well it can give you an advantage on maxpass selections. You can book chracter breakfast for during MM on a day you don’t have MM and they will still let you in for the reservation.
So let’s say that your staying off site and only have one MM. use that magic morning on your first park day- go ride rides, etc. The next MM for
Disneyland comes up 2 days later, but you have already used your MM. you can book a plaza inn character breakfast for during MM. you’ll get scanned into to the park and while your having breakfast you can start making fastpass selections- which will give you better return times for the whole day.
This worked great for us during really really busy Christmas week. We booked a 7:10am breakfast, enjoyed or characters breakfast (we had used our magic morning 2 days before hand) and left breakfast with a couple fastpasses ready to go.