Actually, it is quite strange `Provides:   yast2-installation:/usr/share/YaST2/clients/vendor.ycp` is in two packages: `yast2-update` and `yast2-addon`. And the file is included in `yast2-addon`.

I have checked http://en.opensuse.org/Package_Dependencies#Splitting_and_Merging and it is probably  needed for update.

The file name is not required in any package, it likely does not matter. And it was added in 2007, so for current package updates it is probably not needed anymore.