We can create and update segments based on Declared Id fine. We did find an issue (feature?) where a delivery adds a foreign key (@broadLog-id) to the target schema that you have to remove to get Declared Id segment update working. Once you remove that, the Declared Id segment updates fine.
However, we want to also create an identical AAM segment based on MCID for testing, but AC keeps throwing the error:
There is nothing in any documentation showing how to get MCID segments updating and the datasource just shows the same targeting dimension as the Declared Id segments (Recipient). The only difference in the datasources is the reconciliation key which is [trackingLog/@sourceId] for MCID.