Added the below entry to the 18th Century Trombone History Timeline. I think Mr. Rey may have been on to something.
1799—Paris, France: Jean-Baptiste Rey conducts a revival of Gluck’s Armide. Composer C.H. Plantade, armed with a score of the work, notices that various trombone lines have been added in the performance. Plantade then complains in a letter to the Courrier des spectacles, saying, “masterpieces should be left alone.” Rey replies in his own defense that he sees no problem with enjoying “the full sound-potential” of his ensemble (Charlton).