I did a late September Best of Italy in 2022 and we were in Castelrotto on October 2 and 3. At that time the buses were allowed to drive up to Seiser Alm on Oct 1 so our tour driver took us up there. I do NOT know if that is the case every tour/year. The Seiser Alm Bahn was still running as one of the tour members wound up taking it.
Our group spent most of the day in Seiser Alm. We had a group dinner that night so I expect we went back down about 3P-4P. It looks like we gathered to walk to dinner at 18:40 that day according to the picture of the daily schedule I snapped.
BTW, the year I went some tours stayed up at Compatsch at Seiser Alm and some stayed in Castelrotto.