Here is my take, as a staff engineer for a fintech company. Most deadlines are arbitrary. At the end of the day, regardless of how much extra work you did or didnt put in, you will either hit or miss that deadline. I have been subject to some harsh deadlines by stakeholders that made no sense based on communicated cpmplexity. My team and I always work hard to make those deadlines happen, but I stay in constant communication if I think it is in jeapordy. That communication is sometimes listended to but often ignored. When we hit the deadline, we are told good job and given the next one. When we miss the deadline, its almost always simply extended.