The (שיטה
מקובצת (נדרים כ"ג writes that the origin of
the כל נדרי
goes back to the אנשי כנסת הגדולה.
Of all the Tefilos
& Piyutim in the entire Machzor,
the most problematic and unclear נוסח is the כל נדרי.
The לבוש suggest that individuals should say his
corrected version quietly and not rely on the Chazan's
(Machzor's) Nusach which has no meaning and is like
a bird's
chirping.
For some reason, we don't follow the לבוש and stick
to the נוסח in the מחזור even with all its faults.