Did you actually watch the video?
The only thing being shown is the Pixel having slower/longer animation, and one thing he mentioned is that the 4GB of RAM on the Pixel makes it reloads apps more often vs the 8GB RAM on the OnePlus 6 (which is obvious). He didn't show any actual extreme lagginess other than some twitter comments.
I stand to my previous statement. The OnePlus 6 obviously wins out for now thanks to its more updated SoC and double the RAM. It is already shown many times that the sweet spot for Android is at least 6GB of RAM. Anything less, you end up having to reload apps, creating the illusion of "lag" or slowness.