> Most languages’ baseline sort operations implement quicksort under the hood, including the standard C library’s gsort() and JavaScript’s Array.prototype.sort()

There isn't any "JavaScript's Array.prototype.sort()". Different implementations use different algorithms.

I know V8 used to use Quicksort with insertion sort for (sub)arrays smaller than 10 elements (the implementaion has changed since I last looked, but I don't know what).

But SpiderMonkey has and still does use a bottom up mergesort with insertion sort for subarrays of length 3.