If he wanted "personal free time" without being asked questions, including some pointed ones, he probably shouldn't have taken a car from the service he owns. This person wasn't just "literally" another person, they were technically his employee/contractor and were on the clock even if he wasn't. If I was in this situation where I was working while my boss was technically not but in my presence, I feel like it would be appropriate to ask my boss questions pertaining to my work.