mime support in Ubuntu14.10

I see some wrong behavior concerning mime/Nautilus in Ubuntu 14.10.

I created some packages in /usr/share/mime/packages/ and run 'update-mime-database /usr/share/mime' and 'update-desktop-database /usr/share/applications' afterwards. In Ubuntu 12.04 .. 14.04 everything works fine, the application can be started from nautilus by clicking the corresponding file (with proper file extension and content magic). In Ubuntu 14.10 same procedure does not work!

I try something in Ubuntu 14.10...
1) I try the command 'mimetype' -> mime type is detected proper
2) I try to rename *.odt to *.odx in /usr/share/mime/packages/libreoffice.xml and /usr/share/mime/packages/freedesktop.org.xml. After update-mime-database and update-desktop-database /usr/share/applications the *.odt files are detected proper. I would expect that odt files are not longer detected as Writer document. I also checked it with 'find /usr -type f -name "*.xml" | xargs grep "*.odt"'. No result, but odt types are detected -> why?

So it seems that working principle of mime has changed from Ubuntu 14.04 to 14.10, but I was not able to find any more information in detail.

Also some official packages are effected. For example, if you install geda and create a geda-schematic file you cannot start the geda-schematic tool by clicking the file. In Ubuntu 12.04 to 14.04 it works fine.