C&R Explains Adv Cooling

I'm curious about this comment and how it relates to the 200° comment made by 805moparkid...
“It simply allows you to run a lot hotter safely. But the systems have to be designed to support that pressure.”

Why would you run an engine at say, 300° ? or anything above 220° ?
Does a hotter engine run better, burn fuel more efficiently / completely? and thus more horsepower?

I also want to know what kind of oil they are using that will support +300° without burning.

Also, at that point, ( one would think ) timing would have to be retarded a fair amount to reduce pre-detonation