Messenger to Messenger in Prospekt

Hello Rabbi,

Many poskim wrote that one should not appoint a messenger for a messenger in a prozbul, because the words are not conveyed to the messenger. On the other hand, Tosefta 2 (11:7) “Decrees laws and prozbuls are not written without the knowledge of the two, and Rabbi O’ Um I do not write a prozbul except with the knowledge of the borrower.” And the halachic ruling is based on this, that it is permissible to make a prozbul even without the knowledge of the borrower – according to the Sages, certainly, but also according to Rabbi Yehuda, it is apparently permissible in certain situations.

So, what’s the problem with appointing a messenger to a messenger in Prozbol? Even in the worst case, it doesn’t detract from the fact that Prozbol was made for him without his knowledge, as if he were a person who is not in his presence.