The information you used as evidence in this video is a steam guide and is no way affiliated with valve, here's the link to the guide.

The information on this guide is false, as it says:

A single blast can do up to a maximum of 56 damage to armored enemies and 93 damage to unarmored enemies.

But we know this is false, many of you may remember Flusha one hit killing kioshima with a grenade which contradicts this guide saying the maximum damage a grenade can do to armor is apparently 56, but even if this bug did ignore armor, it still would not be able to one hit kill unless the impact damage happened twice (2x2 = 4, 96+ 4 = 100), however this didn't happen. We clearly see kioshima get hit once for 2 damage and then a 98 in 1 explosion.

However... The guide also says that:

HE blasts will do significantly less damage if you face the blast. As long as the HE grenade model is in your field-of-view, you're facing it. You can receive considerably less damage from a blast by quickly facing the exploding grenade (exact opposite of counter flashbangs).

Simply put, if you look at the grenade you take less damage, now I can't do an extensive research like /u/3kliksphilip , however kioshima is looking straight at the grenade, which also contradicts the guide.

CS Wikia says that 98 damage is the maximum to unarmoured and 57 is the maximum for armored, said here, so if you take that into a point then you'd could say there is a glitch where grenades ignore armor, however looking away/at the grenade to do more/less damage is a little strange and should be looked into whether that decides if you get one hit killed or not. I do recall someone on the wiki getting the exact damage variables from the games files, however I can not find these variables myself, if you do, please let me know.

tl;dr: don't use falsified/unofficial sources as evidence.