In agile processes, like scrum, we tend to estimate our work. Not by time, but by complexity.
What does complexity mean to me?
Complexity is some...
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Estimates are just as much about unknown complexity as well as known complexity. As more information is discovered, estimates should change accordingly.
In Case 1, the actual task has not changed, but the known complexity has changed. This means that an updated estimate will be more accurate. In Case 2, the complexity has decreased because there are less unknowns and the task is much more predictable.
What are you estimating for? If you want a prediction of when new features will be delivered, then using estimates that don't represent the effort that it will take for the team in its current state is not that useful, is it?