Seems like it's designed to make it easy to accidentally send more of your users'/customers' data back to FB than intended. Oopsie!
ie they don't really want your truly-security-critical customer data. But if they can boost their conversion rate with sites like dogfoodreviews.com by 5%, and the price is sending backblaze.com's fantastically-sensitive paid customer data into an unsecured data path, they will absolutely do it.
Comparable to the absolute havoc that Zoom wreaked on browser security to save one click on starting a call.
> ie they don't really want your truly-security-critical customer data.
It's both. It eases implementation with a one-and-done snippet, and then slaps a user-friendly GUI on the other side for marketers to sort through the firehose and use what they want.
While making it also trivially easy for marketers to toggle a button that OKs the turbo-boost mode that siphons up (hashed) sensitive customer information, which can then be used to claim credit for additional conversions by cross-referencing the (hashed) PII siphoned up against what Facebook has for those exposed to your ads.