I disagree. Having a common language in many places has led to huge improvements over the board in the JS ecosystem, it's become the "C" of the modern era, and you can build a lot of stuff on the foundations that others have laid.
That book was created before many alternatives came out; now if you are working in a team project you should look at JavaScript the same way you look at assembler, you know it will be the final thing but you shouldn't be creating it directly, but instead "compiling" from TypeScript, ELM, etc. (langs with no implicit conversions, strong typing, etc)
Those alternatives are nice in startup land, in enterprise consulting land, we get to use what the customer IT department sanctions as allowed programming languages and tools installed on computers for external consultants.
My point is that safety or otherwise of the target language is just not relevant. Even C has compile errors if you use the wrong type for an operation. Assembly largely does not.
Taken to the extreme, any language ultimately goes down to machine code. So if it was a relevant fact, it would be relevant for all languages.
I still hate JS though.