Richard,
I don't understand why you would want all messages, via the settings,
to go only to sender.
If everyone did that the Group would have no messages.
It may have plenty of messages, just no replies. Not all groups are about conversations.
One type of group that customarily operates this way are groups devoted to giving away unneeded items (Freecycle, Freegle, etc.). There a member posts an offer in the group, but all replies, which typically include personal contact info, go to the sender only.
Shal
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