If you expect to be taken seriously, can you please get the
editor's name right? It is Alfred Rahlfs. The edition he
edited was _Septuaginta_, being an eclectic text of the "Old
Greek" Jewish scriptures.
Of course an eclectic text will choose between variants, but
you are imagining things if you think the editor's choice
was made only because it was at variance with the text as
found in a quotation contained in a book of the NT!
Sir Lancelot Brenton's edition of the LXX is based upon a
single source, codex Vaticanus, with some variants from
codex Alexandrinus mentioned in the footnotes, but not
affecting, I believe, the translation, except in a few cases
where the Vaticanus manuscript was mutilated and
Alexandrinus provided the next best text (and these cases
are enumerated in an appendix).
Likewise, Rahlfs' edition is also based upon Codex
Vaticanus, but textual variants found in codex Alexandrinus
and codex Sinaiticus are adopted in preference to those in
codex Vaticanus based upon Rahlfs' critical opinion. I am
very sure he is using standard text critical methodology to
judge which are more likely representative of the "Old
Greek" version used by the majority of Jews.
However, it is certain that all the existing manuscripts
(Vaticanus, Alexandrinus or Sinaiticus) preserve a mixture
of text types (those of the "Old Greek" mainly and of
Theodotian in the case of at least a couple books, plus
possibly others), and several Greek translations of
individual books of Jewish scripture were known to be
circulating in antiquity. Any one of them could have been
used by the author of a NT book.
Are you getting your material from a tract or something?
Cleveland, Ohio, USA