I don't think there is a standard other than your own, what you like and what you find acceptable. Oh, and maybe what your customer requests but that you can steer in any direction you want

What shoe in HMSFM are you looking at?
I use rubber cement sparingly and budget a lot of time for cleanup, one hole at a time. I have seen the top beat sewn on free hand, only once and I would not advise it but it can be done. Leaving it extra wide does also help, that way you can cement below the broguing but it gets harder to follow the topline when you get near the facings.
You could make a top bead of a contrasting color, add a piece of split that's the same as the vamp and quarters and cement that to the top beat, that way the vamp leather will show through the broguing. You'll need a good splitter in order not to have to much material build up on the top bead. Don't know why it's not done. If it's just a shortcut or just not practical to make a top bead that wide with multiple layers to follow the topline.
It would really surprise me if there's not someone out there doing just that. It may just not be any of the makers featured in HMSFM.
Just my

Rob