The Gemara doesn’t discuss it. What I was getting at in my unkempt posting was that it is not a matter of ‘Halacha’, only of effective Teffila. In that case, we look to those who know the ins and outs.
This is not the only issue pertaining to Teffila where we find this. The long Teshuva in the Chasam Sofer about the correct Nusach for us (Sefard or Asahkenaz) does not deal with Halacha per se. He only discusses the Tzinoros, the heavenly paths that each tribe has. The Ri Migash writes about adding parts into Teffilos, that it is not a problem, as long as you keep to the rules of Brachos: The end must match the beginning and the Sheim Umalchus etcetera. So there really is no Halachik (Nigla, solid and absolutely required) issue about the Nus’chaos. Therefore, the discussion is on the basis of what is correct to do.