iPadOS 'Now Playing' Control Question

For context, here are two images displaying my query:

My question is this: Why on earth do I ‘sometimes’ get actual buttons for volume, and other times just a greyed out volume bar in the Now Playing control when I swipe down on my iPad screen from the top?

Is this just a weird CEC/HDMI Control quirk with the AppleTV?

This has been frustrating me for awhile and I realize this can simply be an issue that will never be resolved but I am asking if anyone has more insight into this at all.