If you watch Hotz's streams he takes small breaks to talk with chat and to meme around (just like everyone else during their work days) and he eats lunch and whatever (again just like everyone else).
What I'm trying to say is that Hotz's isn't a superman on Adderall he is just working on stuff he is excited about.
I refuse to believe that 8 hours straight focus every day is common.
I have about 4 - 6 hours of really focused, deep work focus available. 6 hours if I am really interested in the project and 4 hours for normal days. The rest is doing low focus work like writing mail, planning ahead, attending workshops, reading up on updates for relevant libraries, reading documentation etc.
I attribute it to a younger brain, NO internet and NO fun distractions. At 42 I just don't see how I did it, and I know I could never be that focused. Just sitting still for 4 hours make me feel quasy now, and I need to use my physical body in some way.
Now after those I lay down and I can't get up for a couple hours with all this aching in my limbs lol.
A single, continuous 30-minute stint of focus is probably a once-a-quarter event for me.
I've been excited on 10 hours for a long portion of my life. Getting older makes it harder though.