OK, over-simplification. Perhaps: Language in-class variance is small (C# ~= Java, C++, C, RUST are close-ish). Cross-class variance is big (JS vs Rust). There

OK, over-simplification. Perhaps: Language in-class variance is small (C# ~= Java, C++, C, RUST are close-ish). Cross-class variance is big (JS vs Rust). Therefore, recruiting a programmer from the same problem / language class is more important than the particular language.