Media playing after screen locks. S8

[AC Question]

If I am watching a video on my Galaxy S8, the video keeps playing even after I lock my screen. If the video is paused and then the screen locks, the video will unpause and the video resumes. The screen stays black, but you can still hear the audio and when I unlock the phone the video is still playing.

Software version: G950USQU1AQEF
Hardware version: REV1.0
Model Number: SM-G950U
Service provider: Sprint