This affects people who embed artwork but don't use the options you're adding.

Currently, if artwork is downloaded for an album, it completely replaces any artwork that was already embedded in the files. There've been requests for a "preserve cover art" option, but we don't have one right now.

So, with this change, new artwork will get added into the files, and old artwork will never get cleared. The bad part is, it isn't obvious at all that that's what's happening unless you view the artwork tab of the info dialog.