Originally Posted by F.Ultra
However it's not that hard to imagine that Netflix and Amazon has no idea what 24p even is
AFAIK, most if not all of the commercial streaming sites encode most of their material as 24p, some television as 30p and some British content as 25p. For films 24p is what they most often get from their content suppliers to encode so that's the easiest thing to do and it's certainly easy for all of the players to convert into 60p or whatever the connected monitor needs. Surprisingly, they seem to encode most US HDTV episodes at 24 fps; I'd have thought that they'd be encoded at the 60i or 60p of their broadcast encodings. Go to Netflix's site and search for "example"--the first several matches will be various test clips whose titles contain their frame rate: 24p, 25p, 30p, 23.976p and 29.97p.
Something else you might try is to play a title in the PC player, click on the picture to give it keyboard focus and, without blowing it up to fill the screen, type CTRL-SHIFT-ALT-D. This will overlay some text on the picture, updated in realtime--there will be a line labelled "Video frames (rendered/dropped)" where you can read the title's frame rate.