This is simply not true. Yes the numbering system supports what you're saying but you're basing this on zero actual facts. One quick example I can give you is the new 8.0.1.0 mi4c .eu stable, yet there's no such china stable version, but ok, maybe the .eu team has beta testers or rather access to prereleased roms.
The folks at xiaomi.eu are nice enough to provide you with info in build.prop on what china dev version that particular stable is based on. That's just one of many things you can check... and I already mentioned a few out of many reasons why china dev roms are used for modified/custom releases.
If you're talking about kernel versions, you're forgetting that many consecutive versions can have the same kernel version so again this means nothing.
Perhaps we all differ on what "based on" means but please don't go blasting like a little kid for no reason.