Given the Jewish calendar, how would it be possible for these ‘tetrads’ to NOT fall on Jewish holidays?
The three major Jewish holidays don’t happen every month of the 12/13 month Jewish calendar. Those three holidays happen during the month of Nisan (Passover), Tishrei (New Year/Rosh HaShanah, Yom Kippur, and Sukkot), Sivan (Shavuot).
Take a little time to familiarize yourself with the Hebrew/lunar calendar.
You are aware that there are periods of hundreds of years that they don’t occur at all? Did you know that this particular lunar tetrad is the only one to occur during the 21st century? Did you know there have only been 142 of them over the past 5,000 years? Pretty rare, eh?