As of November 2, 2020, when a group member signs up and aligns their billing date with the group primary, if the primary renews within 24 hours, all signup charges for the group member will be skipped. They will then renew at full cost along with the primary subscription later that day.
Previously, the group member would be charged at signup, and then charged again that day for the renewal. This change was implemented to prevent double-charging a subscriber on the same day.