All of that stuff would be in my head, but not written down anywhere. Even when I co-taught with other faculty we didn't make lesson plans. Instead we planned in advance in office visits, divided up the work, and then we each had ownership of our own piece. Common exams forced some integration of those pieces but within broad guidelines we were free to vary how we covered things based on our own discretion.
More recently, I've been involved in a week long professional development activity for learning technologists. I've done that for each of the past three years as one of the six "faculty" for the institute. We do a lot of planning for this and in the planning the lead faculty and the organization that sponsors the institute want plans for each session. Part of the reason for the plans is to communicate to the others what is intended so they can comment and advise. Another part of the reason is to create assurance that we're ready for the sessions. Here is a plan for a sidebar on budgeting I did. I ended up not sticking with the plan. And I never told the joke on opportunity cost. In fact, I'm not very good at sticking with a plan. I know that if I'm over prepared I'll be stiff. I don't want that.
But we are going to have teams conduct class sessions. Lesson plans make sense in that context, for communication among team members and as a getting ready activity. I will try to model that for you, though there is certainly room for improvement in my demo. For instance, I note that I've got a bulleted list there, which I critiqued elsewhere, wanting sentences instead. Let's see if with the next few there is improvement.