ChrisAyers - Oh, right. Ok.
I think I understand why Microsoft didn't include it (I bet it has something to do with permissions and/or the nature of the external accounts using a Shared channel).
We enabled shared channels in December 2022 and within a month we wished we had not. We enabled shared channels because it solved two problems for us: 1 - Teams tenant switching and 2 - guest account provisioning.
However, it didn't have all of the functionality we needed for external collaboration forcing us to keep guest account/external sharing, so we now have another layer of complexity - external sharing/guest accounts VS Shared channels.
Now, both of our original problems are being solved in other ways: 1 - Teams tenant switching will be mostly fixed with the new Teams client by the end of the year; 2 - guest account provisioning is solved for us with cross-tenant sync (our biggest external collaboration scenarios are from mergers and acquisitions).