When you assign a person to a problem (hr policy, infrastructure scaling, new UX capability) they will treat that problem as most important, and if then they break it down a certain way and delegate parts those people will do the same with their respective parts. Like a game of telephone eventually what's actually important and what people think is important will drift apart, and before you know it a lot of people are working and doing stuff that doesn't really matter or is even counter productive.
A founder who can hold the whole business in their head and inspects the whole company at all levels continuously will spot and challenge/correct these drifts.
I think it was from Creativity Inc I read that Steve Jobs would challenge engineers about things and if the engineer stood up to him and made their case and it made sense and fit into the vision Steve would commend them and give them the autonomy, at least for that decision/project, but if the engineer folded or couldn't make a case for why it was the right decision he would steamroll them.
So I think founder mode is basically inspecting and challenging the company at all levels to maximize progress towards realizing a vision, and only people who are great visionaries and can also understand and judge the vision-alignment of unlimited micro decisions across many disciplines are able to operate this way.
