Coming late to the thread and replying both to the OP and to this ^.
That’s my beef with Roon’s library management even the vaunted Classical Music management. THIS ^ is not knowledge. Is just statistics. Obviously Suesmayr “standing” comes from his Mozart’s Requiem completion and its popularity. Same for Klopstock - he is the author of the verses of Mahler’s Resurrection… so it gets picked up with it, given that the metadata credits him. True classical fans with real knowledge do not do this - yes, they know Klopstock did that. BUT - not a factor in our libraries…
Unfortunately, not sure if this will ever be solved to my satisfaction… not with public metadata - just give us the option to have our metadata as the only source of truth… purty pls! 
Love Roon otherwise… don’t get me wrong!
v