Interesting. And it is also true that as SimonP said 'routepoints' don't actually have to be unique Id, apart from within their own route - but in practical terms (eg Mapsource) it's easier just to assume everything should be unique.
One 'mistake' that I often counsel against, is people plan separate routes in separate .gdb files, and then try to combine the two or more projects at the upload stage or by copying all into one gdb file. It looks as though the upload method might actually work (but the end result might not be very helpful visually) - but combining into one gdb is usually doomed to failure, unless you're extremely well-organised. Much better to work in one big gdb file from the get-go, for big multi-route projects like tours.