Yes, definitely - I think you may not have read my post completely. Note, I said either as an embedded id3 tag or a .id3 file
The id3 files (not embedded tags) were introduced for those file formats that were not compatible (or supported in LMCE) with embedded id3 tags, such as flac and avi's etc. That is their entire purpose. UpdateMedia looks for these as well, esp on the first scan - if they already exist, then it simply imports the metadata from them rather than creating new ones (in fact it never creates new id3 files for this type of media on the first scan - as there is no metadata in the database already for the new media file, and there is no id3 file, then there is no metadata so it doesn't bother to create an id3 file)
I have a fairly large collection of MP3 files. I went thru the web admin to tag them properly, and things showed up nicely in lmce. Unfortunately, upon a reinstall, none of the change stuck.