Charlie, I think you are missing the point.
You do not need $5000 CPU.... All you need is 8-16gb of RAM on $150-$300 computer

A used i7 Thinkpad would be great example of that.
10-15 years ago, I can agree that would be a "brilliant" approach. Now it would considered to be a very sloppy programming.
The only point where I can agree with you on this is to have this feature available for people who are using 10-15 year old computers. For vast majority there should be a choice, an
OPTION of choosing between rendering from hard drive
OR doing the process in memory.
Adobe and other software companies had this option for over a decade to choose how processes are handled.