The short answer is that we should eliminate the 20% rule, which would eliminate those questions. Then you simply rely on the definition of registral activity in the statute, which involves a communication between a public office holder, for compensation, and an employee or consultant, about one of an enumerated list of decisions or the arrangement of a meeting.
The complicated analyses of travel time and prep time were introduced in the calculation of the 20%. Eliminate the 20% rule and you eliminate all those confusing questions.