Almost every B2C company I’ve worked at, I’ve written or had my devs write proxies for whatever trackers we use. The reality is that every company to whom this data matters to figure out their business model will proxy their trackers. If they don’t they need to fire their lead engineers.
It’s actually pretty easy to disguise this traffic even to the point where you can use the originating server/cdn to interleave the tracking with the content source.
It’s not about serving assets it’s about hiding telemetry from adblockers, dns filters, ip lists, etc.