the suggestion wasn’t meant to be perfect, and I’m sure others could have stated it more clearly the first time
virtually any message circulation function could be handled by exchanging emails among a defined list. So why join Gio? Just “reply all”.
this is just a suggestion that would be very easy to direct msgs to certain lists of group members that would be clunky doing it via subgroups. Could it be done via subgroups? Sure, but one could also say why hashtags? Just create a subgroup for different groups of topics. That’s an absurd example but it meant just to point out that anything can be done another way, even if that other way is more clunky.
(Believe it or not one of our Y! group members got fed up and started his own site a few yrs ago — and set up separate message exchanges for about two dozen types of topics (essentially hashtags). Mannnn what a PITA mess that turned out to be.)