Yeah, it seems a bit hit and miss whether 5.1 is a factor in low volume…
Watching a TV show with 5.1 lke Reaper, it’s relatively quiet and I turn the volume up a little.
But then watching a film with 5.1, like Batman, the volume is LOUD!
Checking the Netflix forums, historically there have been issues with specific titles having unacceptably low volume. I agree; either Netflix are ripping them oddly or the source material just has unusually low volume.