I’m not sure what you consider the conclusion to be, but large-scale refactorings at Google do happen in the way described in the article, with the bulk of the migration done using many commits done in parallel.

Being able to rollback is indeed important and reducing the sizes of commits makes it less painful. If one project has a problem, unrelated projects won’t see the churn.

Or at least that’s how it was done when I was there. It’s been a while.