Good video. It's a similar result to what I've got when I've chopped a lipo with an axe or knocked a nail through. It's a little frustrating to be honest, I originally hoped for a fireball like you see in some videos, but 99% of the time all you get is a lot of white smoke and maybe, if you are lucky, a small flicker of flame. Yet i've seen batteries go up in flames spectacularly after a crash?
I think maybe the fact that a lipo is old and has very high IR might make them less volatile. This could explain why sometimes in a crash they burst into flames yet it's so hard to reproduce that same spectacular result with old batteries.
Tony, if you want to get 'pyrotechnics' you might try deliberately over charging an old battery... Stand well back!