That is orthogonal to part-time. Even with part-time you can agree on a common core time where such things can be handled. I also had cases where timezones were

That is orthogonal to part-time. Even with part-time you can agree on a common core time where such things can be handled. I also had cases where timezones were quite useful. (In the evening I sent work of the day to QA and in the morning I got a test report to work on) My concern is around all the non-core tasks, which you can't cut away proportionally when working less time, leaving overproportionally less time for the core job.