How do you know? Have you tested it? No.
Has anyone tests non-host against non-host? Probably not.
All these videos prove is that host has an advantage, which has always been there. And 100ms really isn't that much to complain about since a typical reaction time is somewhere around 300ms.
All I know is that it doesn't work against me particlularly (nor drop shotting) and I find it a bit ridiculous although very satisfying to kill these players. They are making such an effort that it makes it all the more fun to get the headshot (I get a lot against drop shotters it seems).
LOL. How do you know? Has someone proved it?
Yes, several people have proved it through understanding how a hosting network works. Since all information goes through the host, any in game lag the host sees would only be multiplied from on player to another. No one has to prove something that is common knowledge.
As for the other guy, I already explained that if you are appearing in the wrong place, you are pretty much invincible because the enemy is shooting in the wrong place. Obviously you are still able to take damage from explosions, or maybe if the guy shooting at you aimed off target and just so happened to be in the direction that you went.