...sometimes people will ask me "can you get this done by [time]?" and I'll say something like "seems reasonable" but as the discussion carries on, it becomes clear that they want me to basically *promise* that I'll get the task done by then.
I think you're right in this diagnosis, but I don't think that this is strange or unreasonable. In complex organizations, people do often need to know with reasonable certainty that someone else's task will be done by a certain time. So in many work cultures the counterparty is actually asking "can you promise to work as hard as it takes to get it done by X time", not asking for a calibrated estimate for how long it would take when you're working an average 40 hour week.
I think you're right in this diagnosis, but I don't think that this is strange or unreasonable. In complex organizations, people do often need to know with reasonable certainty that someone else's task will be done by a certain time. So in many work cultures the counterparty is actually asking "can you promise to work as hard as it takes to get it done by X time", not asking for a calibrated estimate for how long it would take when you're working an average 40 hour week.