Comment by noisy_boy

I think PMs fail to understand categories of change in terms of complexity because they focus on the user facing surface and deal in timelines. A change that brings in a big feature can be straightforward because it perfectly fits the existing landscape. A seemingly trivial change can have lot of complexities that are hard to predict in terms of timelines.

There is also the angle of asking for estimate without allocating time for estimation itself.

For lack of a better word, I think it should drive from "complexity". Hardness of estimate should be inversely proportional to the complexity. Adding field to a UI when it is also exposed via the API is generally low complexity so my estimate would likely hold. We can provide estimate for a major change but the estimate would be soft and subject to stretch and it is the role of the PM to communicate it accordingly to the stakeholders.