Besides the fact that he might not want to, I suspect many FAANG companies aren't optimized for hiring developers capable of making something like Photopea. Very little about the hiring process at somewhere like Google or Facebook is about what you can make on your own.

FAANGs hire for people who can make a small part of a larger whole incredibly well. That's mostly good for what they do, which often requires deep knowledge of specialist algorithms, but they miss out on hiring generalists who aren't necessarily good at the deep stuff but who can make lots of simple processes work well together. Which,in my opinion, is what you need to be a good front end developer.