Hi @mbosman
Welcome to the Auth0 Community!
Please allow me some time to research the options that we have in this case and I will be back as soon as possible with new information.
Just wanting to verify, both of the linked identities come from the same Connection, correct? In case the Connection is different for the users, it is possible to verify via event.connection as mentioned in the following topic : Linked Identities - which was used to login?
Will be waiting for your confirmation, thank you for your patience in the mean time!
Gerald