I have just mistakenly discovered that a two finger double tap can resume playback of Netflix when it is running in the background.
I realize that this gesture is the standard play pause gesture, but I didn't know it would work for Netflix when you are at the home screen or your iPhone or iPad is locked.
Tried and tested method:
1. Begin playback of a show or movie in Netflix.
2. Press the home button.
3. Perform the standard two finger double tap, or press the play button on your headset if applicable.
4. If desired, lock iPhone or iPad.
Hope this is of use to someone,