A straight "Reply" to a groups.io message in e-mail always goes to the entire group. That's the way message lists/groups work. The options at the bottom of each message presented as links are for when you want exceptions to the default behavior.
--
Brian -Windows 10 Home, 64-Bit, Version 1809, Build 17763
If you remove all the homosexuals and homosexual influences from what is generally regarded as American culture, you are pretty much left with Let's Make a Deal.