The AR Platform is a very reliable and accurate platform if well put together and well maintained. What these tests show is that an AR will shoot until failure, on full auto, and will do so reliabily.
When your non-free-floated handguard catches fire, you MIGHT want to consider an upgrade, but not before ceasing to fire full auto.
Another good reason, a stellar one actually, on why I recommend building your own weapon! You know how it works, and you know how to maintain it.
These videos prove that knowing your weapon is FAR more important than who's name is on the side.