This means Netflix operates as a production and post studio for their many and talented film-makers. The stuff with the red N on the poster -- some of it is REALLY good -- uses Netflix-operated handling. Any video production goes through a lot of steps from raw studio footage to edited, finished product. This web site says that Netflix processes and people handle a lot of that. Also it looks like 4K is their minimum…
When you used actual film it was long lengths of the stuff, hence footage. Lots of words have weird no longer relevant sources. Like “logs”.
log (n.2) "record of observations, readings, etc.," 1842, sailor's shortening of log-book "daily record of a ship's speed, progress, etc." (1670s), from log (n.1). The book so called because a wooden float at the end of a line was cast out to measure a ship's speed. General sense by 1913.*
So it does have a relationship to the wooden log - it was originally a series of measurements from a floating bit of wood.