In all fairness, the waving of handkerchiefs this time was very much a greeting from the international delegates and the rest of the audience, and was not directed at Sanderson. I'm not even sure he was still on the stage at that time. In contrast, the Chautauqua Salute pre-1916 was definitely a greeting in honor of Pastor Russell. I recall reading in P.S.L. Johnson's books that it was considered presumptuous when after Russell's death, the Chautauqua Salute was given to another speaker, like only Russell could receive it. Johnson was so fixated on Pastor Russell that he was shocked when someone else was saluted in this manner.
I don't know when the Chautauqua salute was purged, but I'm sure that by the mid '30's when the flag salute issue came up, anything with the name 'salute' had to go.