Typically, I would agree. Yet, I'm fairly certain Google has good reason for doing so.
In any case, the simple fact that the reasons are unknown speaks pretty heavily for the case that the reasons aren't universally valid, so you would be learning a dialect of C++.
Google documented pros/cons and reasons for their decisions in their style guide, which is public [1]. Whether or not Google's final decision is applicable to you, reading the pros and cons is informative. For example, their reason for not using exceptions is specific to their existing code base [2], but the discussion is informative.
[1] https://google.github.io/styleguide/cppguide.html
[2] https://google.github.io/styleguide/cppguide.html#Exceptions