Alan Kay having 4-6 hours a day to read books is certainly out of the ordinary and I can't emulate that. That's not "work day" - that seems more like "I don't have to go to work"-day. I suppose we can acknowledge that Alan Kay is making use of his time wisely.
Also, what kind of books are we talking about here? I guarantee you Alan Kay is not reading a technical book like Compilers by Aho in a day. Sure, he might be physically able to read the letters on all the pages in the book, but he's not LEARNING that much information in a day. That book is 2 semesters worth of new information, not to mention that it requires practice to solidify.
Even the author acknowledges this is a case of quantity over quality. How much actual learning is Alan Kay doing? Now that would be a useful point of reference. That would tell me if I have to up my learning game or if I'm doing just fine.
If every week I learn one new technology like RxJava, React Native, P, etc, am I beating Alan Kay at learning, even though I might be reading fewer pages?