Pretty cool. I wish I had known that trick a few months ago when I was stranded after my pump broke while simultaneously braking the stem of my replacement tube. Doesn’t look like you’d get a great seal, so I’m curious how high you could get the pressure.
I thought I might as well try it. My joeblow pump doesn’t lock on the makeshift adapter so, I had to hold and push hard. I would imagine people would have trouble there. It took less than a minute to get the tire to 90psi with one arm pumping.
The guy in the video uses a hose with a compressor on the other end. Does he care if the seal leaks? Probably not.
Screw-on Presta adapters are cheap; buy one (or two); keep one with your bike.
Some modern pumps come with a flippable connector that gives you both Schrader and Presta connections.
Then there’s those English valves… what’s a trick for those?