I think it is is in how a writer uses the time they have on a movie or show.
The biggest challenge a movie has is limited to three hours to tell the story. You have to have an arc, some climax and resolution so the development gets truncated. A great writer or director uses this economy wisely telling you as much as possible in the brief time they have. This is why "show, don't tell" is important because twenty minutes of pure exposition is exhausting to sit through. The character design, fashion, expression, speech, even their musical theme tells you a lot quickly.
Shows can delve deeper showing a more protracted and natural development of a character arc, but they have to keep the attention of the viewer while doing it. This can lead to more fulfilling payoffs, but it can also cause filler issues in the story.
Many shows I watch I think if each episode by the end needed to be there. I enjoyed Jessica Jones, but you easily could have shaved two episodes off and nothing be lost and it would have better pacing.
One thing I hope the Black Mirror model shapes is not being stuck making episodes a set time frame. Maybe Episode one is 72 minutes, episode 2 is 37, episode 3 is 55, etc. Have the story come first rather than constricted by outdated constructs of how television use to be. this is mainly for streaming services like Netflix that don't worry about time slots and commercial breaks.
