Thanks Cassie. Already done, the same day: I submitted it through the Developer Feedback form on 31 August with the follow-up opt-in ticked, and it covers the five points you list, including the CRM_UI comparison and the sourceLabel absence. Flagging it here so nobody waits on me to send it.
One thing has been added to the case since. In the v4-sunset thread /automation/v4/flows/performance has no dated successor ahead of the v4 sunset a suggested workaround was to use property history with AUTOMATION_PLATFORM plus the flow id. That is this same missing field: someone who knows the API well reached for it as the obvious route, and it is not there. Worth adding if the submission reaches the team.