Not sure what's cool about that. A fork is a patch set, with a ton more ergonomics on top. Passing around sets of patches was what we did before VCSs were common/easy-to-set-up, and it was always brittle and annoying.

Here is a homework for you to see why they do it:

  1. Checkout Chromium's codebase.  
  2. Make a commit and see how long it takes.  
  3. Try to push it to any git hosting service.  

You will discover what's actually brittle and annoying.

And yes, being 10s vs 10000s devs in the same repo isn't fun.

Standard practice for Chromium forks. Chromium's repo is huge, slow, and impossible to diff for your changes with 10000s of other commits. Also, painful to host it anywhere.