Yes - for some of these you can stream if you know the URL, but you're only able to discover the URL after making an account.

I think a number of these are also public rebroadcasts piggybacking off a less-public source.

Definitely a lot of these are also [re]broadcasts from vendors, probably for a specific platform or distribution target, that people found the URLs for and that the original source isn't super aware of the details of

If they contain some entropy, i.e. if there's path/parameter based bearer token authentication, sure.

https://iptv.example.com/720p.m3u8? I doubt you'll convince many courts of that being nonpublic.