[glenjamin]

I see the "sweeping change" argument put forward often, but I don't really understand how this can be the case.

There is no atomic deployment of a large distributed system - so even if you can check in related changes in different areas of a codebase, how do you release them?

[Smudge]

Solving deployment is orthogonal to organizing your code. You can deploy multiple products which share the same codebase, and you can also deploy one product which draws from multiple codebases (say, from other gems or npm packages that you also maintain). Regardless of where your code goes, handling distributed releases generally requires agreed upon contracts (e.g. schemas) and proper dependency management during rollouts.