For example mathlib doesn't develop basic theories like Riemann surfaces, and doesn't have Riemann existence theorem etc. So if you develop a complex analysis result without these there are many things you can't even talk about. Developing basic theories takes time and efforts. See Anthropic FLT proof for example. While 13 million lines headline count may contain 50% redundancies due to agent swarming, on the net they still dedicated millions lines of effort to develop basic theories. And often they developed specialized versions in concrete theories just sufficient for their needs. For example they still don't have Riemann surfaces nor Riemann existence.

13 million lines?

And people laughed at Doug Lenat and Cyc for wanting to encode all knowledge as a set of rules.