Just been looking at Mozart’s Great Mass in C Minor. OK, it’s an incomplete work, but curiously the MB work names refer to this explicitly, but only at (some of) the lowest level - e.g. Mass no. 17 for Soloists, Chorus & Orchestra in C minor, K. 417a/427 (fragment) “Great”: IIa. Gloria: “Gloria in excelsis”. The word “fragment” does not appear in the intermediate and top level work names.
It seems to me that the naming should be consistent and my preference is to delete the "(fragment)"s, but I thought it best to consult before editing such a canonical work.
I’d agree about deleting “(fragment)” from the low-level work names. It’s certainly inconsistent not to have it at the higher levels too, but I don’t think it should really be part of the title at all.