Nobody is claiming the iPhone X is slow. But there is a clear competition, and consumers are involved in that, cause if they are told by the manufacturer "their phone is the fastest", consumers don't want to spend that much money just to find out another phone proves it wrong.
Yes, we can all be mature and civilized about something as non-important as electronic products. But that's not reality. The reality is consumers feel better when their product's manufacturer's claim are completely true, and feel worst about a purchase when it's shown it's not. If the video showed the other way around, the Note 8 would get slammed by the same iPhone X users saying that it doesn't matter.
That's just how it is and how it will always be.