Today, I checked the data for typhoons that also include this September.
Looking at the data for September alone, the number of typhoons formed has been trending up modestly since 1951.
However, during this September four typhoons formed, which was below the 1981-2010 mean value of 4.8.
Also the number of typhoons formed from January through September between 1951 and 2020 shows a downward trend.
You can also see a downward trend by looking at the annual data up through 2019.