The confirmation email now reads
"Thank you for your interest in Groups.io and the group [xyz group]. To complete your subscription, please reply to this email."
This is misleading when the group is restricted. It sounds like replying to the confirmation email "completes" their subscription. I suggest changing this to "To confirm your interest in joining, please reply to this email" or something along those lines.
For years I've been unaware of this language, and I just discovered after running an unrelated test. It might even account for the frequent failures by pending members to return required questionnaires.
Messages are the sole opinion of the author, especially the fishy ones.