There seems to be something trailing the falling rocket in that video. A small parachute?Here's the video. The MLRS footage starts around 0:57 mark:
After reviewing the footage, I'm not sure if it's the PCL-191. The MLRS appears to have boxy-looking launchers, whereas PCL-191 has tube launchers. Perhaps the combination of video resolution and the distance from which the video was taken causes the launcher to appear boxy, I'm not sure. However, the 8x8 vehicle appears the same as that of PCL-191.
Anyway, the video is about testing new ammunitions in high-altitude conditions to ensure reliability and performance. It's not clear if the footage of the MLRS is stock or not.