“They came back differently” should not mean “we forgot who they were.”
The common miss: A shopper arrives from Meta on mobile, joins the email list, then returns on desktop. A system that only sees the email record or current device may fail to suppress them from another prospecting ad.
The Triple Whale path: Pixel triple IDs, customer IDs, emails, and event context can resolve to one global identity, making the exclusion audience more complete.