AVPlayerInterstitialEvent.Restrictions don't work on iOS 15.1

Specifically I am trying to set .constrainsSeekingForwardInPrimaryContent when creating an AVPlayerInterstitialEvent but it has no effect on iOS. I don't have access to tvOS at the moment to try it there but according to the docs it should work on iOS 15 and >.

let event = AVPlayerInterstitialEvent(
  primaryItem: App.player!.currentItem!,
  identifier: ad.podId,
  time: CMTime(seconds: ad.timeOffsetSec!, preferredTimescale: 1),
  templateItems: adPodTemplates,
  // sadly on iOS these restrictions seem to simply not work
  restrictions: [
    .constrainsSeekingForwardInPrimaryContent,
    .requiresPlaybackAtPreferredRateForAdvancement
  ],
  resumptionOffset: .zero,
  playoutLimit: .invalid)

Thoughts?