This is at least the case for Office and .txt files on my installation
If you run ShellExView and sort by Type, what's listed with Type = MetaData?
Microsoft Office Metadata Handler
Microsoft XPS Shell Metadata Handler
Pinned Site Shortcut
Those shouldn't affect .txt files at least.
Have you tried with a new .txt file just created in your Desktop folder?
Actually, you are right. The problem does not include .txt files.
This is actually not a big problem for me and I was just flagging it. Happy to provide more details if you like though.
Empty (0 byte) Office files are invalid, which is probably why the Office property handlers don't let you set a rating property on them.