I suspect it's because HR doesn't know the difference.

It is easier to learn C++ if you know C, but it's a good point, they're not the same languages, and have diverged greatly over the years.

I would understand that back in the days of C++98, but C++11 and newer are really very different languages. Proficiency in the earlier language specs doesn't guarantee any such in the newer specs -- as I learned when I came back to dev work in C++ and had to update my skills quite a bit working in C++11 (I learned C++98 long ago and had worked exclusively in that for quite a while).

I remember in grad school in 2005/2006, I decided to write a little program in C++ which I hadn't touched since the 90s. The language had evolved enough that I found it to be enough of a challenge that I ended up writing the program in Perl instead.

Even as a C++ type I still shudder when I see Perl.

A lot of companies use both C and C++ on different projects, sometimes due to use cases and requirements, sometimes due to the preferences of the project leads, sometimes due to legacy code bases

It's not hard to train one from the other, but very hard to train a JS programmer into a C programmer.

Someone I knew claimed he used to be a C+ programmer.

You get taught C++ on the job