Yup. Mine only cast from YouTube Plex and websites. No other apps work like CTV, CBC, UFC.. Nexus player and shield don't do this, they are always visible. You can enable developer options and enable always on. If it can't sleep it won't disappear.

Yes you've gotta grab the remote and turn it on before it will show up as a cast device. I've also noticed the casting isn't quite as reliable as my gen 2 Chromecast. I've had Netflix fail to start playing video, NBC will exit the stream in the middle of an episode, etc.

Given the choice I have been using the Android TV apps over casting where available. This isn't always an option though since some apps I use don't have Android TV versions.