You'd be surprised the garbage overhead brings into an app architecture...
These best practices really only make sense in large organizations, i.e. Conways law.
After all, you can't really ask 100 developers to all add code to one file in a couple weeks - they will spend a month or so just resolving conflicts...
100 file repos are designed so that 100 developers can edit them (in theory), and have relatively few conflicts, not because its better code.
As another anecdote, I find whenever I do solo code I can easily spin out thousands of lines of code within a week (includes testing), when doing code on a project with many other devs my rate drops into the range of maybe 200 a week, just because so much time is spent interlinking other code, finding fixing bugs and tests strewn across many files...
