I thought it's a good illustration of how fractured and fragile the JS "library" situation is. It's a bit like the previous PHP standard library, combined with the worst of Perl's Tim Toady.
The reason I say it's a strange example is because of this: https://github.com/tc39/proposal-string-pad-start-end, which was added to the language two years ago (and seemingly very quickly [as tc39 proposals go], I assume due to left-pad)
That's a strange choice of example to highlight the sparseness of the standard library.