What is special about Bärenreiter Urtext editions?

Gabriel Fauré: Requiem

Gabriel Fauré, Messe de Requiem op. 48 (version de 1900)
Music samples 1 and 2:
I  Introït et Kyrie, T. 49-52, autograph score
Trumpet and horn parts added by the composer in pencil writing

I  Introït et Kyrie, T. 50-54
Music sample 3:
Bars 51 and 53 in the second bassoon part were missing in the first publication. The edition follows the printed orchestral parts thereby reconstructing the bars.