I've been using iTunes since, I think, version 6. If I recall correctly Album Artist was introduced in version 7. Before that iTunes had issues whenever there was a guest or featured artist as that would break up an album into multiple parts. Even when Album Artist was added they didn't copy the behaviour to iPod classic, so if you wanted neat listings on that you had to use the same value for artist across an album, or use the part of a compilation option. If you read through my article Grouping tracks into albums you should see that there is a switch under View > Column Browser > Use Album Artists (use the Songs view if needed to access this option) that modifies the behaviour of the Artists section slightly. With it enabled all values of Album Artist are listed, otherwise it is all values of Artist. I recommend this option is switched on as that gives views where complete albums are listed in one place in list.
I'm not quite sure when the sorting fields were introduced, but they were there in iTunes 7 when I got seriously invested in fixing up my library. When sorting a view by artist it is typically the order I gave previously, i.e. the first non-empty value from Sort Album Artist, Album Artist, Sort Artist, and Artist. I've not double-checked, but presumably when Use Album Artists is not in force that might switch to the first non-empty value from Sort Artist and Artist. There used to be some right-click options that would let you set sort options on a single track, and then apply these to all tracks with matching primary values across your library, but they seem to have disappeared at some point. I will typically use the column browser and step through artists and albums where I can quickly spot and correct discrepancies.
I think the main thing to understand here is that metadata is messy, and generally inconsistent. If you want things to be neat and tidy you cannot rely on perfect data coming from the iTunes Store or the Gracenotes CDDB database, you have to put in some effort, tweaking spellings to make everything consistent, and setting custom sort values if you want artists sorted by their surnames, etc. And each time you add new items to your library you may need to make corrections so that they follow your house rules. Consistency is key. I have a number of scripts at https://samsoft.org.uk/iTunes/scripts.asp that I've written over the years to help myself and others apply such rules more efficiently than is possible by hand.
I use Apple Music and don't seem to have any particular trouble editing metadata to make my library the way that I want it, however there is a potential issue when you've edited metadata for purchases as this can sometimes revert to the information held in the store. When I spot this I hide the purchase from my purchase history so that my own matched copy has precedence.
I have sometimes called iTunes the logic puzzle that keeps on giving. Just when you think you understand exactly how it works Apple will make some change behind the scenes, and it is time to adapt again.
tt2
