> Have you written significant amounts of C or C++?

Yes.

> Most of the time when someone says something is "written in C" it actually means it's C++ without the +± features.

Those "someone's" have not written a significant amount of C. Maybe they wrote a significant amount of C++.

The cognitive load when dealing with C++ code is in no way comparable to the cognitive load required when dealing with C code, outside of code-golfing exercises which is as unidiomatic as can be for both languages.