When is playbackBufferEmpty triggered? Why is this property YES observed from the observer method when returning to the foreground from the background even if the buffer is not empty?

Apple TV + Apple official 'https://apps.apple.com/tw/app/id1174078549 ' is normal operation same as iOS 17

Is there any update for iOS17 in FairPlay? So far I have found no relevant information. iOS 16 is fine