You need to put this in perspective though.

The use of Lithium Ion packs without a BMS (battery management system) is fool hardy as they have the potential to be explosive as shown if they are the variety based on a Cobalt cathode. The later and current compound cathode types are far less likely to explode as shown in the video.

Lithium Polymer referes to the type of construction of these batteries IE Soft cell pouches not hard cased cells, as they are soft walled they can be punctured and damaged so should be encased in a secondary box.

As I mentioned above use without a BMS is foolish as issues with the cells occur when they are discharged too far and then on the subsequent charge cycle they can, if the older cobalt types, cause a fire.

All the horror stories came about in the early use of them by RC enthusiasts who didn't use a BMS and didn't use the correct charging schemes.

The modern compound types are far more robust and feature fusible links for short cct protection but still need a BMS and correct balance CC/CV charger to ensure a good cycle life...