I would certainly hope that all founders have gone through these questions in detail, and may even internally have it written down (even if they didn't call it

I would certainly hope that all founders have gone through these questions in detail, and may even internally have it written down (even if they didn't call it a business plan), but I guess in an "interview" people might (accidentally or intentionally) paint things very rosy, and sometimes as the owner of the plan you can stare yourself blind in the details.. Having someone like PG question and unpack things in real-time would probably be priceless for most startups! Also remember that when you invest in great people as much as (or even more than) ideas, then the moment-in-time plan matters less/differently somehow.