They mean HLS When/If they notice you're not using HLS instead of some other solution like MPEG-DASH, they will raise a stink and force you to fix it. I know

They mean HLS When/If they notice you're not using HLS instead of some other solution like MPEG-DASH, they will raise a stink and force you to fix it. I know this because I had the privilege of changing a video playback stack to be 100% HLS over a weekend for a fairly big name app when it became a Pri 0 issue thanks to Apple noticing the app hadn't been using HLS 100% of the time during a minor update. There's also verbiage requiring a laughably low bitrate stream as a fallback. Our users would file bugs when we fell back to that stream instead of audio only since we had a rich audio only mode they preferred given that the video at whatever bitrate (192kbps?) for our content was nothing but a colorly mess. This was years ago, the rules are still in the app store, but I have no idea how well they're enforced anymore.