I know that it's supposed to but it just does not. I spend more time curating my library than actually listening to it so it's very frustrating for me. I love so much about Plex - in fact pretty much everything else - but the fact that it will ignore/override my tags (that I spent days and days (ok weeks) doing for some 500k tracks) drive me up the wall.
now here is my tagscanner shot - note the year on the album (this is also included in the title because this artist had trouble naming his releases so there are several self titled albums)
And here - Plex has decided (via Gracenote I am assuming) to override my year - my copy is a vinyl rip - it is not ripped from the CD release decades later - and truthfully I don't care when the CD was released, - I want to use the "decades" search sorting so I am more concerned about when the original music was released than I am a particular copy.
Sometimes it even over-rides album art, sometimes it over-rides album title and matches an album to something it's not.
I work very hard to make sure my tags are perfect - I'd be super happy if Plex would read them and only pull information from other sources if it is missing from the tag (it's not)
I think if Plex could fix this issue on the music side, then it would be practically perfect in every way.
[Side note - this could possibly be, in this instance, because the album release date is just Year format in my tag, but truthfully, unlike movies, the full release date string of Year-Month-Day is unnecessary for music and is frequently something that is not known except for new releases]