In a reply to a recent tweet Diablo Community Manager Adam Fletcher / Pez Radar confirmed that the issues with how Sundered Charms were working in Diablo II: Resurrected’s 2.5 PTR will be fixed on go-live. We’ll get details when the patch notes come out. But, it seems likely that they WILL work with minions and pets when released.
(When asked if the issues with Sundered Charms not working with pets and minions would be addressed.