Microsoft Teams cloud calling/graph-is there a way to have a bot add a PSTN participant to a meeting?

Question

Using the C# calling SDK for Graph, I can join a bot to a meeting, and add participants by GUID from the same tenant. Where this falls apart though is adding a participant from PSTN/direct routing. If I have a regular user add a participant, I see this update:

          "@odata.type": "#microsoft.graph.participant",
          "info": {
            "@odata.type": "#microsoft.graph.participantInfo",
            "identity": {
              "@odata.type": "#microsoft.graph.identitySet",
              "phone": {
                "@odata.type": "#microsoft.graph.identity",
                "id": "+19054181287",
                "identityProvider": "None"
              }
            },
            "endpointType": "default"
          },

Seems reasonable enough, so I tried adding a participant like this:

            InvitationParticipantInfo target = new InvitationParticipantInfo { Identity = new IdentitySet(), };
            target.Identity.SetInAdditionalData("phone", new Identity() { Id = targetID });
            target.Identity.AdditionalData["phone"].SetInAdditionalData("tenantId", m_tenantID);
            target.Identity.AdditionalData["phone"].SetInAdditionalData("identityProvider", "None");
            target.EndpointType = EndpointType.Default;
            await call1.Participants.InviteAsync(new List<InvitationParticipantInfo>() { target });

Which generates a request that looks like this (interesting that the identityProvider changed):

"participants": [
    {
      "@odata.type": "#microsoft.graph.invitationParticipantInfo",
      "identity": {
        "@odata.type": "#microsoft.graph.identitySet",
        "phone": {
          "@odata.type": "#microsoft.graph.identity",
          "id": "+19054181287",
          "tenantId": "8c6ae172-a3ea-4f50-994d-a0256822697f",
          "identityProvider": "(Generic: l3QstqQ1)"
        }
      },
      "endpointType": "default"
    }

And that comes back with this:

Action failed: 81bd4426-7200-4c50-acba-f17b7a987322
exception: Code: 7505
Message: Request authorization tenant mismatch.
Scenario Id: 46ffbff3-bf9f-4b6d-a639-974c07b959dc
Inner error:
    AdditionalData:
    date: 2020-10-13T18:45:30
    request-id: 5d152942-dc10-4baa-bb28-48bf991f944b
    client-request-id: 83f84370-3708-4e3c-a34d-2f69bd8eb8a7

Given that the meeting organizer has permissions for PSTN dialout, as do invitees, is there a reason that a bot shouldn't be able to add a participant like this? What's interesting is that something very similar does work for redirecting/transferring incoming PSTN calls. The "Request authorization tenant mismatch" seems like a red herring (since it's all the same tenant)-is this just a case of "not supported right now"? I know PSTN calls from bots are (still) not officially supported, but I was curious whether anyone had a way to make this work?