that is expected
i can guess that they think that when user use fullscreen then he/she do not want to get interrupted as you know if someone play it could be annoying to get ads that could hide part of your screen
But I find it really special because I use Brave on my phone and my Ipad, on this device you can only be in fullscreen and I receive rewards but not if I’m playing or watching a video so I don’t really understand why it’s not like it on MacOS and why there’s not an option for it.