AVPlayerItem incorrectly emits an initial value of true for isPlaybackBufferFull

I've noticed a discrepancy when KVO monitoring the playback state of an AVPlayerItem in iOS 14.3 for an HLS source.

Whilst monitoring AVPlayerItem.isPlaybackBufferEmpty, AVPlayerItem.isPlaybackBufferFull and AVPlayerItem.status fields I'm seeing the following during video initialisation...

iOS 13.3

isPlaybackBufferEmpty "false"
item status "readyToPlay"

iOS 14.3

isPlaybackBufferFull "true"
isPlaybackBufferFull "false"
isPlaybackBufferEmpty "false"
item status "readyToPlay"

You'll notice that in iOS 13.3 no value changes are observed for isPlaybackBufferFull, whereas in iOS 14.3 isPlaybackBufferFull emits a true value followed by false. That doesn't seem correct?

I've also raised this with Apple's Feedback Assistant FB8941944.