That is NOT a how-to on a leak down test. The reason it is named a LEAK-DOWN test is because you pressurize the engine and see if it LEAKS-DOWN. You're haphazardly finding leaks by squirting liquid into the hole long enough to keep the air out. The only leaks you can find like that are huge gasket leaks (and not even all of them).
I traded a guy last month a cylinder because his nephew drove his blaster into water. He four point seized the engine and the momentum of the assembly sliding to a halt broke one of the mounting tabs off the cylinder... It can be done, air cooled 2 strokes can take some beating but enough cold liquid ( I agree, probably not 7 shots of windex) sprayed straight down on them WILL take its toll on an engine.
Also, it's not just the piston you're looking at damaging like that... The base gasket mating surface is just above the "track" which captures oil and funnels it down to the crank saddle bearings. When you sprayed ammonia based windex onto that gasket and the engine shut off, guess where that windex that got sucked into your engine ran down to? Straight into the crank bearing possibly washing off lube. Do THAT enough times, crank bearings will be harmed.
If you're going to make a video and call it a how-to, do the process correctly.