That first one is laughable, it is from a biased source and is intentionally rigged to produce the desired result. They present it as if the overpressure relief valve is the only probable leak point, and set it up to immediately ignite before any real volume of gas has time to mix with air. It's like lighting a gas range in a kitchen immediately after opening the valve, and claiming this proves it would be safe to let gas leak out for half an hour and then light a match in the same kitchen. Of course you get no explosion when you carefully make sure the conditions needed for an explosion don't occur, by igniting immediately at the leakage site.

The second one is more interesting. Here, they do in fact allow the gas to mix with air for a few seconds before ignition. However, these tests used liquid hydrogen at a much lower temperature than the gaseous phase cold compressed hydrogen we are discussing here. Liquid hydrogen is seriously cold, and only boils off to gas phase at a slow rate depending on how much heat energy it can absorb from the surroundings. In that sense liquid hydrogen it is rather similar to liquid gasoline; it's the gas that burns not the liquid. You'll note none of the spill experiments in that video involved pressure vessels rupturing or pressurised fuel lines breaking, it was all liquid hydrogen at atmospheric pressure. That makes a huge difference in how rapidly it mixes with air. The very low temperature also slows down the reaction when it is ignited, compared to igniting gas that's a hundred degrees warmer.