There is a registry data bug during the QuickPatch Uninstall ?

I Explain my case :
I have a Full MSI that create registry key and set data to this key.
I make a QuickPatch to Update a data value of this registry key. The update of the data value is ok.
When i uninstall my QuickPatch, the old value don't come back and the entire value of my registry key is removed.

For files, when i uninstall my QuickPatch, the old version of file is restore with no problem. Why it does not work with registry data value ?

Thanks for your reply and sorry for my bad English.

Best regards,