Hi Amber! I really like this approach. Could you please share your Smart List and Flow logic for the internal campaign? I'm assuming it would just be "Member of List" in the Smart List and then "Send Email" in the Flow, but would like to confirm. Thank you!
This should be the answer to this question (IMO) @Amber_Hobson suggestion for using a specific campaign for the seed list is a great workaround to this issue.