Fwiw, if you pull apart the HLS manifest that Apple TV produces for any of its shows, you'll find ad stubs injected by the manifest server (independent of the preroll promotions). This isn't unusual in and of itself, but it does indicate that ad decisioning is something they've designed for in their play stack even now. (for those unfamiliar with streaming, an ad decision point is basically a stub in the playlist where the player will call back to the server and accept playlist fragment insertions, generally representing ads)
From a technical standpoint, the only really interesting thing about this is the fact that it isn't using Apple's own HLS interstitial support (which is the Blessed™ way of doing server-guided ad insertion on HLS), but rather their own weird custom thing afaict. But from a business standpoint this is interesting because it kind of tips their hand: ads are coming eventually, even if Apple hasn't said anything about it.