Honestly, I don’t know. I’ve never seen it used at night. But WP produces extremely thick smoke, and I’m not seeing any. That could be an artifact of the video, or it could be something else.
Use of WP against a civilian population is a violation of the Law of Armed Conflict. It’s use against a military target, however, is not. WP is useful primarily as a screening agent, and secondarily as an incendiary. It’s useful as an antipersonnel weapon against troops in the open, but then again, ordinary high explosive is better.