Y_orange,
you will be surprised with my findings.
VLC may be using mozilla agent, but it appears to be "mysterious" to servers.
Here are examples, first gospel music:
winamp
VLC
Streamlink's work looks to me to be something like rtmpdump's work.
Rtmpdump saves stream to disk or pipes it to player.
Streamlink pipes output to VLC.
When you play the stream directly with VLC you see stream's url in VLC's title bar and no user agent whatsoever in urlsnooper.
AlJazeera: VLC, direct connection
When streamlink plays the stream you see fd://0 - VLC media player in title bar and User-Agent: python-requests/2.18.2 in urlsnooper.
Giniko, streamlink, VLC
Challenge still remains. Urlsnooper has to show VLC as Mozilla everywhere.
When I get m3u8 from Giniko urlsnooper shows curl. Giniko likes curl, just doesn't like nothing that VLC shows.