This is a nice trick but I'd definitely avoid doing this if you actually have the time (and specific mechanic) to ward properly. If you have any ability that can withhold vision within the fog of war (for instance, Lux's Lucent Singularity, Ashe's Hawkshot, Quinn's Heightened Senses etc), it can act as a temporary ward for you to actually ward safely, properly. If you watch the video in its entirety, you'll see that honestly, it gets the ward in there but not much else, the vision for many of them are very limited. If you feel immediate danger, do this, that's fine, don't risk dying to ward properly, but if you feel safe and are able to reveal parts of the map, I'd suggest you ward at the furtherest edge/corner of certain brushes; that way you can get a lot more vision.
Another 'trick' that this video didn't show specifically is that, if you click on your trinket or hold down whatever key you bind to your trinket (and whatever item slot you may have a warding item), you'll be able to see the "aiming reticle" of your ward/trinket. What some people don't know, is that it goes green in a brush. As such, if you hover your mouse over the edge of a brush, you'll always be able to tell whether the ward is going to be in the brush or not. Nothing's more embarrassing than placing the ward just outside the brush.