I do the same has you. And like Myrkul said, some booklets are aliens and don't follow that rule because the guys or are analphabet or just dumb.
My rule when I'm organizing my booklets, even if there is no numbers on the pages, I count then as the universal format "Booklet front/ Booklet 02-03" and so on.
When I have booklets with the pages numbered in them I organize them as they are.
I tend to be to much perfeccionist in that.
PS: Page -1 is interesting XDXD