You can be skeptical, but this has been tested empirically. Defect density per lines is relatively constant (this is a well-known empirical result, which you can also google), which means more lines predict more bugs. When researchers contrasted line count vs bad modularization, line count was the better predictor (precision & recall).

Maybe it's anti-intuitive, but it's what reality shows :)

> in my observation bugs tend to sit between modules due to bad interface design

Yep, and when you start ripping the monolith apart into separate version controlled projects and deployment pipelines without addressing the interface issues you've significantly increased the complexity of your work products.

Keep in mind that size doesn't necessarily equal complex. Where I have seen Conways law most clearly is with dysfunctional teams regardless of size.

I was on a team once where one of the senior people was such a jerk no one wanted to work with him. This led to him and the team carving out a piece of the system that he alone worked on and interfaced with the rest of the system through a single queue. This was certainly not the best design and added all sorts of unnecessary complexity.

Another team I was on had a person who was a good programmer and tended to blow off design meetings. The organization never rarely reprimanded this person. In turn it led to various APIs being built that were close, but always not quite right.

Big company examples abound. Contrast and Apple keynote to a Google one. Sometimes I wonder if the people presenting at the Google one even work at the same company.