The real problem here is the leadership deficit. The manager got pushback on the estimates, and instead of explaining the reasoning and bargaining on scope, he caved and kicked the can down the road by letting the estimates crumble. Yes, estimating is hard, and you are probably going to be wrong, but once you have your finger on the scale to get a desired result, you can't blame that on the difficulty of estimating. Just deplorable leadership.
Because it feels good to complete work and I would like to move on to other features. How long can you work on improving a single piece of code before getting bored?