That's an important point. Maybe as an academic someone is more inclined in learning new languages for the sake of intellectual interest, but on the engineering side, having uniformity of language is a big plus.

I ask myself, by the way, if the author misses the point not considering that all code that the programmer writes is translated in machine language / byte code of elementary instructions: those instructions are the primitive language. But the programmer uses a more elevated language as he wants something more expressive.