Property "Title" In Pictures Folder/library: More Than One Tag Read?

On various pictures, I've seen it read the XMP "Title" tag, the EXIF "Description" or "User Comment" tag, the IPTC "Caption" tag, even Keywords or Sub-categories.

So my question is, what's the limit to it all? I would think that "Title" would only display a metadata tag with a similar name, like XMP DublinCore Title, or, if it could only find its IPTC counterpart in a file, Fixture Identifier. I suppose that when you don't give yourselves all that much space to work with, as is the case with the bottom panel of a Windows 7 Explorer window, doubling- and tripling-up like this can be considered practical. Maybe I haven't looked far & wide enough. All the same, I think that a tooltip or some easily-gotten-at description of the fields in that bottom 3/5 of the window would be more than enough to satisfy one's curiosity.

I won't add mischief to misery and ask "Why was this done?" as I've already partly come up with a reasonable answer myself (available space within the bounds of the window). I'll just ask if anyone else has been curious about this, and if so, invite them to comment here on this thread.