В статье к записи с Каррерасом есть упоминание об этом:

When it was decided to perform and record Rossini's "La Pietra del Paragone" the only immediately available scores - piano scores at that - which came to hand were Friedrich and Gunter Rennert published by Barenreiter. RAI, the Italian Radio Corporation kindly put a tape of the Scala performance of 1959 at our disposal and a friend loaned us another private recording of a later Neopolitan performance. It was unnerving, to say the least, to find that neither scores nor tapes corresponded with each other with any degree of regularity. So the obvious next move was to resort to the autograph. I wrote to the Ricordi Archives and was told that they did indeed possess the Rossini holograph - but furthermore they would be happy to put their performance materiai used for the 1959 Scala performance at our disposal. In due time the orchestral score arrived for perusal. But here too it was clear that various numbers had been omitted and certain sections cut. Therefore it was most necessary to go back to the holograph. Here again, Ricordi most kindly provided us with a microfilm. With this in hand, we proceeded to restore the missing numbers -in particular, the gardeners' chorus, the introduction to the first act finale and Fulvia's aria. The exact order of sequence was established by the help of an early libretto in possession of the Library of Congress in Washington. Aside from certain minor cuts and the deletion of several recititives, the work is presented in its entirety. Throughout the opera the original orchestration was restored.
Newell Jenkins