"Seat time" is literally what you are giving them in that situation. You can say that it's not "time" but I can say that it is because there is nuance and we are doing many things at same time. Being present physically, mentally, paying attention to your surroundings, putting in effort, etc, can in many ways be counted separately. Who's to say if your way of accounting for time is the "correct" one or whether somebody else's is?

Eh, I see what you mean but I think in this culture and point in time, it's useful for human well-being to see them as separate things. Like I said, conflating them is a sleight of hand. Because the reality is that you can book 1h for a meeting and then be totally mentally absent from it. People think that you're committed in the meeting, you're giving it your time as can be measured. You are not actually giving your time to the meeting but due to being physically present, you're also not using your time (and attention) freely on what you really want to. So you're doing a sleight of hand possibly on yourself and people observing you in the meeting.

Then why are they still paying me for it?