Purely guessing: abstracting a browser name is yet another abstraction layer. A later that is not needed by chromium. Maintainers of chromium primarily care about maintainability of chromium, not other forks.

If the browser name is referenced in multiple places, it seems to me that by defining it in one place actually increases the maintainability.

I think what they're saying is that Chromium will remain Chromium, so maintainers have little incentive to worry about this