Wouldn't most carriers have peering relationships with Apple for Apple TV content? Presumably iCloud Private Relay traffic could be sent over that connection as well, meaning that of all the VPN-esque solutions, Apple's is the most efficient from a traffic exchange perspective.

(Of course, it was likely never about the traffic exchange itself, but rather the ability to route, shape, and track traffic dynamically on a host-by-host basis, as others have speculated.)