Sure, most of them have docs in some non-English languages, but rarely all of them. And things like StackOverflow answers, bug reports and discussions, tutorials, and blog posts tend to be mostly in English. Autotranslate works to some extent but can be misleading or confusing when dealing with specialized terms that aren't well represented in its corpus. My Japanese coworkers certainly need to be able to comprehend written English.

Sure docs for massively popular libraries are translated but think about using autocomplete, reading the actual library code, or even just reading other code in your organization. I have to imagine it would be difficult without any English proficiency.