The shortages are for lower end laptops and tablets and peripherals like printers, not for the entire market or any desktop PC's really. I purchase equipment for the company I work for, and even during the height of the shortages, there was no issue buying $1000+ laptops. Under about $600 and it was nearly impossible to find anything for awhile. Even now, Dell is backordered for a month on all their lower end laptops. It's not that people are upgrading from 6-9 months ago, there's been a huge shortage and people are still trying to get systems that they've been trying to get for 6-9 months.I totally understand why somebody with an old low-end computer would have upgraded last summer when suddenly they have to be on it all the time.
It doesn't follow why the kind of person who uses a PC for 10 years would want to upgrade again 6-9 months later.
It also doesn't follow that there's a "backlog" for WFH and education, because since when do coorporations and schools buy high-end cutting-edge components? and why would they be buying them now and in 2021, instead of when this all started?