Commentary for Berakhot 84:11

היו יושבין כל אחד ואחד כו': הסבו אין לא הסבו לא ורמינהו עשרה שהיו הולכים בדרך אע"פ שכולם אוכלים מככר אחד כל אחד ואחד מברך לעצמו ישבו לאכול אע"פ שכל אחד ואחד אוכל מככרו אחד מברך לכולם קתני ישבו אע"פ שלא הסבו

If men were sitting [at the meal], each one says Grace for himself. If they were reclining, then yes; but if they were not reclining. no ! Against this I quote the following : If ten were journeying by the way, although they all partake of one loaf, each of them says Grace for himself ; should they sit down to eat, although each eats of his own loaf, one may say Grace for all. Note that he here states "they sit," i.e. although they are not reclining !

Abraham Cohen Footnotes to the English Translation of Masechet Berakhot