Use of templates isn't frowned upon. TMP is frowned upon because usually the performance gains don't justify the loss of readability. It has been said many times in many ways: don't write code for yourself, write it for others.

Basically, Google has an enormous code base. Stylistic decisions should have semantic weight, but since everybody has their own style, it becomes challenging to understand the reasoning behind certain choices. When you have a standard, it means that you can read into some of the stylistic decisions sprinkled throughout the code.

Take for example, the use of pointer arguments for passing the addresses of results. The justification is that using a pointer is explicit and unambiguous. Non-const references have value syntax but pointer semantics, which can be confusing. Yes, this is contrary to some of the core values behind C++ but Google felt that the improved readability was worth that dissonance.