But those hours are very blurry and come in random high bursts („being onto something“). They’re important and effective for me but it’s difficult to categorize them or even track them.
There's maybe a slight argument to be made for meetings, but even then you're supposed to be paying attention to the meeting, if not then why are you there? One person might need to take notes...
I have more important things to do, like doing actual work.
The difference is that in the office people pretend to be working.
If you work for an agency, and sales is having a tough time closing a deal so there's no work for you today, but you have to be there anyway, ready to work or finding other things to do, maybe upgrading your tools, practicing/learning, then that's still work time. It's not leisure time.
Just because you don't achieve 100% uptime cranking out widgets non-stop at full productivity doesn't mean you're not working. We're people, not industrial factory machines.
You can say 'people are pretending' or 'that's not actually work', but it is. And saying that it's not is just denying reality by casting a moral judgment on it like that.
I agree with you that sitting at my desk or being in the office is work time regardless of what I am doing and therefore should also be paid.