"No, it's less effort than that"

Engineers have been burnt by too many ex-engineer PM's who haven't coded in 20 years, but push back against estimates by claiming "I could've implemented this in Perl in 2 hours. How can it be 2 weeks!?!"

So it depends on who's saying "no, it's less effort than that".

Often I come to my engineers and say "No, it's less effort than that" because I know "You've never done this before, and you're buffering for the unknown. But actually one part of this can be reused from <module> and you can get this other part from <existing service>". I share the context, the engineers go "oh cool", and update the estimate.

And just as often I come to my managers (people and product) and say the opposite - "No, it's more effort than that" because I know what other things the devs are working on that are not visible to the PMs, what scaling cliff they're stopping us from going over, or that the PM's t-shirt size is not including automation, testing, infrastructure, scaling, etc.