This a great rule, and it's good to have it spelled out. So often people skip discussions of records or books because they don't know them when you can get to know them by coming to the discussion.

I run a very successful short-story group on Zoom that operates under guidelines similar to yours: 1) you don't have to have read the story and 2) somebody who has read it and knows it well speaks briefly about it to the group. That way you can always learn from attending a discussion.

We've also found, as your group has, that if you want to attract people with day jobs in different time zones, late Sunday afternoons are the best (and maybe the only) time that will work for everybody. You just have to hope, if you're in the U.S., that the people you want to attract aren't pro football fans.