I would argue that any company with enough JavaScript developers will eventually develop JS libraries too. There's nothing that limits this to just C++. Facebook has folly but also react and a whole set of tools around it.
Framework in JS, is just similar to a more abstracted library in C++.
In the whole stack (or spectrum) of machine, language, application, C++'s design philosophy naturally encourage things like Folly and Absl. Just like JS encourages React, VUE etc.
Also yeah, every reimplementing jquery would be extremely strange and mostly defeat the point of jquery... which is to not have to implement jquery's constructs in Vanilla JS
Most C++ shops don't have their own equivalent of Folly, they use Boost or Google's Abseil or something else.
So people extrapolating from a ~100 person company or a ~1000 person company using JS might as well think it's about the language, but it's really about the size, I think.