I would guess that's when the Cambridge Analytics thing became well known, where they were using Facebook's network/data graphs to compile their own compiled and targeted data.
Nothing. Because TikTok didn't put the tracking pixel there, UberEats did. It's from an advertising campaign that UberEats is running on TikTok. The need to related "conversions" (ie: people ordering/buying shit) on their system with whichever ad they were given on the TikTok side.