I didn't say "write 50x more code" I said "gets done the work of 50 average people". Think of all the meetings, admin, HR, accounting, meetings, stand-ups, one-on-ones, architects, code reviews, process improvements meetings, directors, and meetings needed to staff 50 engineers. Think of how much time is spent just keeping them vaguely aligned. For 50 engineers you need at least 4/5ths total effort just into keeping everyone and everything in sync and moving forward. There's tremendous waste.
It's not hard for one or two decently talented engineers to accomplish more in a year than 50 people.
I have worked with those people and most of what they created was a heap of code that someone had to maintain after they left.