Yes, it true, if you use Python you can rewrite portions in C to get improved performance. But my point was rather that you couldn't later decide you should have written the entire project in another language like Rust or C++ or Java or Go. You've got the make decision about your primary language up-front.

Or to look at it another way: Python with C extensions is effectively another language. You have to consider it as an option along with Pure Python, Rust, Go, C++, Java, FORTRAN, or what have you. Each language has different trade-offs in development time vs performance.