My two cents, the earlier a project is in its development, the easier it is to write tons of code for it, so something that started out as a personal or three guys project ends up having 80% of it all written by them. As it matures and is used in production, adding more code becomes a lot slower, as there are more things at stake, there is more concern about breaking stuff and, simply put, things just keeps getting more complex. At this point, each developer usually writes the same amount of code, that's why you get the angry looks when you ask.

Besides that, from time to time you see the mythical 10x engineer, that guy that simply plows through code faster than anyone else. It exists, but is far from the norm and, in my experience, it usually does more harm than good.

Most 10x developers also think their solutions are always the best and tend to overtake all demands and not let other people code. It gets detrimental really quickly and the situation grows to a bottleneck around that guy pretty fast.