What you describe,Jerry, is a good safe way to go and get good results, but it would be very time consuming if making a lot of drawer boxes. And I might add that most lock miter joints are made on end grain. If a box beam or pedestal, "L" shaped corners etc. was being made it might be used on edge grain. For me I use one pass and as long as it is clamped tight and fed at a rate that sounds and feels good there doesn't seem to be a problem. Cutting them freehand is another matter. I have only done it in plywood though, maybe solid wood is different.
I might add that doing numerous set-ups creeping up on it lends to chances of a screw up, for me.
So far the majority of the miter lock cuts that I have needed to do were long cuts with the grain, by long I mean about 20", the length of the corner styles for the cedar chest. These cuts are much different that the end grain cuts that you have described I suppose.
If what you are doing works well for you then of course there is not need to do what I described, but I have not, as yet anyway, been able to make the long cuts that I described to my satisfaction. That's why I tried to do the sneak up thing.
I am anxious to start trying to cut end grain again. So far, the few times that I have tried to cut into end grain I have not been able to it to my satisfaction. Clampping is the big issue, especially if the work piece is narrow and/or short, say only a couple of inches wide and three or four inches long.
As far as being time consuming, I probably have more time than good sense, so time is not much of an issue for me, but of course that can change.
I believe that sometime way back I told you that I wanted to make some sort of a sled for the end grain cuts but have not figured out how to approach the problem yet.