I don't think the point of lowercased's comment was that devs don't underestimate tasks to the same degree that "outside-of-technical-people" might. They are saying that "outside-of-technical-people" don't have the experience to understand how difficult it is to give an accurate estimate or how much pressure is put on devs to agree to a deadline and take responsibility for making something happen by that date. This is compounded by the fact that stakeholders are unwilling to define or commit to a detailed set of features or acceptance criteria. The bigger the project, the more painful and difficult this becomes. Stakeholders say "Make it faster!!!" then engineers say "We agree!!! any ideas on how?".
That's fair - my intention was to say that non-engineers aren't any worse than engineers. I've seen the same puzzled look and demands from development teams that are requesting changes from other development teams.
Open source projects are rife with developers demanding the near-impossible from contributors/maintainers, etc. (but plenty of examples people not being dicks as well)
Additionally, they can often be worse (toxic) about it precisely because they are developers themselves, and so think they have that understanding and start acting the alpha.
