In Tagalog: "Madali lang naman diba?"
Probably one of the most annoying things a programmer can hear, especially from a client or a manager who has no appreciation of how complex software development is. It's presumptuous at best and actively damaging to schedule and morale at worst. We already know estimation is hard, there is no need to make it more complicated by automatically assuming the best-case scenario (or in many cases, an impossible scenario)
The problem is that it's a jedi mind trick that can easily work on the weak-willed. It's a bad form of programmer hubris coming into play: Newbie or junior devs looking for a chance to prove themselves enthusiastically say something ridiculous along the lines of "oh sure, i'll just need to floobify the crominator function a bit, should be easy", and the crafty manager gleefully ticks off that part of the schedule as "on track"
Better managers will instead ask the question "How long will this take?" And if the reply feels like an unusually low or high amount of effort, the manager will follow-up with a clarification as needed. "Really? I thought it was a simple UI change?" or "Really? I thought it would be more complicated because we have 12 such screens right?" The intent of such clarification should be to elicit more information and not to pressure the dev into giving a more "desirable" estimate. Eliciting information also helps to find any differences in understanding which may be affecting the estimate. If the estimate is still unsatisfactory after clarification, the manager can ask the dev to study it further or get a second opinion as needed
And if the dev is unable to give an estimate immediately, the manager should avoid pressuring him to do so, instead giving him some time to study the problem more thoroughly. "Can you get back to me with something rough, say by tomorrow morning?"
Understandably, clients and managers have this pressure of trying to fit all the work within a chosen schedule. But such should be anchored in reality and not reliant on pressuring devs to say that their work is easy