If you add up every "new customer" your platforms claim, do you end up with more than your actual order count?

Been staring at this all week. Meta attributes a buyer, Google attributes the same buyer, Klaviyo attributes them a third time, an affiliate grabs some of the credit and the sum of everyone's "new customers" exceeds the total number of orders that actually happened. Which is obviously impossible but it's the data most brands set budgets on. The only way I've found to cut through it is new customer acquisition cost (nCAC) measured against real orders deduped across every channel, new vs repeat split at the campaign level so each new buyer is only counted once no matter how many platforms raise