"Template meta-programming" and "templates" are very different. Further, the style guide says "avoid" but does not forbid it. Clang-Tidy doesn't throw up any warnings when using things like std::enable_if.

My codebase overlaps with the majority of your tenure at Google. We are in google3.

I do agree with the guidance that things like SFINAE should be avoided in general, but I believe you've way overstated the rigidity of the guidance.