Thats rather an assumption and not borne out by the data in the database, maybe experienced MusicBrainz editors are using it, but more casual editors certainly are not, and it certainly cant be assumed by the CSG. I dont see an explicit ordering when you add advanced relationships so I wonder if the order is the order they are added or the order of the relationship type, i,e does conductor always come before orchestra, or only if you add conductor before orchestra.
But anyway in this discussion https://community.metabrainz.org/t/why-don-t-classical-releases-have-track-artists/97385
although there was no agreement about changing things I think there was some agreement that 'track artists' do exist for Classical just as they do for Pop/Rock its just that they are involve more people and there are some grey areas (but there are always grey areas). Clearly if added manually I wouldn't add a performer to the track artist if they did not perform on that track but this is all clear from the release cover/liner notes. And the recording relationships do not provide a great alternative because:
- they allow performers to be added who are not credit on the release cover/back (but did play) to be added
- recording artist relationship artist credits are recording level not track level (as chirlu mentioned in another post)
- no order defined
So whilst recording artist credits could often be the same as the recording relationships they are not necessarily so.
If we think about it from a tagger perspective using ID3v24 for a second just to make my reasoning clear
For a Pop/Rock album the track artist is clear and would go in the TPE1 field, there may be many additional performers credited on the release and added as advanced relationships , but we would not them added to the TPE1 field, they would go in the TMCL field.
For Classical, there are clearly some performers we would want added to the TPE1 field (the conductor would not, they would go in the TPE3 field), and there are other performers who we want in the TMCL but not merit going into the TPE1.
The logical split is the between those artists in both recordingartistcredit and recording advanced relationships and those that only go into the recording advanced relationships but this distinction will not occur if recordingartist is generated from the recording advanced relationships.
But that is in the Release Artist section not the Recording Artist section