Did you already know those to be System files (and if so, how?), or did you hypothesize that that was the case (and if so, whence came your intuition?)?
I was almost certain they were. Preference files are considered "system files", and these are essentially preference files even if not in ~/Library/Preferences.
A "system file" appears to be anything that a user would not normally open. Thus, a "system file" is pretty much anything that is neither a document, an application, nor a folder. Anything in /System, /private, /bin, /sbin, or /usr is also a "system file" unless you start the search inside the folder. (From within /System, a search for filenames containing "Finder" turns up /System/Library/CoreServices/Finder.app even without looking for system files.)
But I hate the taste of egg on my face, so before posting I did a search in ~/Music for items containing "Library" in the name (so I'd have a conveniently short list), and tried it with and without system files, to confirm that I would be giving good advice.
