Teams-only experience from contact card across Office

Running an extended pilot for a client, noticed a weird behavior when the user is in Teams-only upgrade mode (but not the tenant Global upgrade policy).

Opening a contact card in any office app (most often, Outlook) and trying to send an IM or call a federated user from another tenant doesn't work - literally, nothing happens when you click the IM icon or ... -> Call option.

Presence is also not displayed in the contact card outside of Teams:

Teams is set as default IM client for Office, obviously. And it all works perfectly for internal contacts (both Teams-upgraded and Skype). Wondering if I'm missing something here or is it just not a supported integration option?