No. That does not mean they have to program in both languages. If the programmer only understand one language (which would be a shame), then they only need to program in their field. This increases the talent base, not reduces it. C programmers do not need to be a Rust expert, so what in the world are you saying there? They just need to cooperate!
Top paying technologies interestingly has Go, Rust and Zig almost same medium salary, and very close (in that order). Immadiately followed by “Bash/Shell”? Yet, the most used languages such as Python and JavaScript are way down. Funny how Bash and Shell scripting is more used than Java, C#, C++ and C, while on the same time earns more money than those languages.
Can you make a living as a “Bash”/“Shell” programmer? :D