Yes, it is the difference between "in theory" and "in practice". In practice, almost no one would write the C required to keep up with the expressiveness of modern C++. The difference in effort is too large to be worth even considering. It is why I stopped using C for most things.

There is a similar argument around using "unsafe" in Rust. You need to use a lot of it in some cases to maintain performance parity with C++. Achievable in theory but a code base written in this way is probably going to be a poor experience for maintainers.

Each of these languages has a "happy path" of applications where differences in expressivity will not have a material impact on the software produced. C has a tiny "happy path" compared to the other two.