IIRC a big part of Google’s coding guidelines is also about making it easy for people not heavily invested in a specific language to contribute safely. So not necessarily a project size but rather an organizational concern.

They’d rather see it done the same way it would’ve been in any other similar language than with a language specific feature.

There are also portability concerns in mind given that projects like Chromium have to be easily portable across a vast amount of platforms (this shows with things like long long which is also on the list).