This has nothing to do with NNTP, BT, P2P. All FXP to distributed FTP servers. The RARs are split so that if one server in the farm goes down, the whole release isn't corrupted. Same for transferring the data.

"Racers" move the els to multiple servers. Split RARs allow for multiple people to be moving parts of the same els at the same time.

Everything about the scene is for non-torrent sharing (atleast public / largescale distribution). The scene groups hate public torrent sites/users.

I don't think there are messages with more than 500k on NNTP, a single RAR file won't fit (so theoretically you could encode a 700M file in yenc).

That's why you use yenc. Personally, I believe it's to do with now bypassed limitations of parity programs.