It is entirely reasonable for the business to say "we need X in Y weeks" — it still might not be possible, most of the time engineers can make _something_.
What's unreasonable is saying "we need X in Y weeks, and it needs to be done properly". It will take a certain amount of time to do anything properly, and that doesn't change with pressure.
As a manager when I've pushed back on estimates it was because the engineers were pushing for "done properly". Where "done properly" didn't mean more features but building a more solid foundation. And I 100% understood the desire, but at a higher level the long term cost of not having that solid foundation was worth incurring.
What's unreasonable is saying "we need X in Y weeks, and it needs to be done properly". It will take a certain amount of time to do anything properly, and that doesn't change with pressure.