Yup, my boss at old co had some similarities to Greg. He worked long hours, was pretty much aware of everything happening at the company both in the US and off-shore, could talk technical details with the tech peeps, and business stuff with the non-tech folks. He was always on top of things and unblocking people all over the org. He also has the great ability to remember things very well, even after a few months have passed by.
Even though he was CTO and incredibly busy, he would find time to spend with individual engineers. Once he spent an hour pair-programming with me on a difficult issue. Even though his time was obviously not spent coding (and hadn't for years), it was a very productive session.
The founder acknowledge he really couldn't have done it without him, or someone like him on the team. I 100% agree they couldn't have built the org without him. He is just on a different level and it was awesome seeing him in action.