I don't really like Rogan personally but this behavior is intentional and quite smart in my opinion. Rogan (and his team) preps quite a bit, the vibe he is going for is an everyman who does not know anymore about the situation than you do. This is not reality. The idea is that this style makes the listener not feel stupid or embarrassed to learn about the viewpoints of the interviewee. He's among the most listened to interviewers in the world, so I guess it works.
"His listeners get him, like him; maybe even want to be him. He's not a show-pony, or a light-entertainment phoney: he's the all-American do it yourself modern man, tough but intelligent."
In a 3 hour interview format, I don't think he really needs to. The interview itself is a similar medium, and by not already knowing all of the details, it probably makes it easier to genuinely bring along listeners from zero information to a full picture.
Does he lie when he claims he has? I've heard him discuss books with guests on many occasions, though I'm sure he hasn't read everyone's books given the number of guests he has now.
High profile guests, long form content. Rogan's not really a great moderator (for example, he doesn't even read the books of his guests). He's not asking insightful questions. He can even be a bit dense. But he's open-minded, curious and "normal".
If I'm settling into some work and don't want to listen to music, I can put on Rogan and know I've got 3 hours of filler. You can pay attention only to the parts you want to and not be concerned you're missing anything important. After hundreds of hours, part of what makes it special is continuity and familiarity.