Anytime,

If you want to know more about newsgroups you can find the structure here: https://www.itpro.com/infrastructure/network-internet/368089/the-big-8-usenet-newsgroup-hierarchies-and-what-they-cover

And you can find information about the file encoding here: https://en.m.wikipedia.org/wiki/YEnc#%3A~%3Atext=yEnc+is+a+binary-to%2Can+8-bit+encoding+method.

You are wrong. Usenet uses Network News Transfer Protocol (NNTP)  and newsgroups are Basically just forums with different topics.

Usenet is basically the first ever worldwide forum or discussion system and it only accepts text, it doesn’t accept binary. Files are posted by encoding files as text and posting them, but since there is a size limit for each post similar to twitter, the files have to be split.

Your ISP can see that you are connecting to a Usenet provider and if you don’t use SSL they will see what you are downloading, but it doesn’t matter since in most countries only sharing is illegal, downloading is not illegal.