In the first video, they said the shell on that one was thin because it was simply a demo model- a desktop showpiece, not meant to be test-fired. That and it was undersized- it was meant for a .223, but they fired it on a .308.
Basically, I think it was gonna 'splode no matter what, but yeah, with enough hot gas the metal part was distorting, the plastic didn't stand a chance.
I'd be curious to see how a "wet" can performs. There was an article in a magazine years ago, about a very James-Bond-ish .25 or .32 (probably a Walther or similar) sold in a 'kit' with a tiny stainless steel suppressor. I seem to recall it was about the same diameter and just a tad longer than a "C" battery.
But the only way to make a can that tiny work well, was to run it "wet"- that is, containing a fluid that helped cool the hot gasses. As such, it was supplied with threaded plugs at both ends, and fitted into an ankle holster rig.
Which tended to make me wonder- that's not really a... you know... self defense type rig, is it?