Widely used libraries have one more constraint, in that they will always be used a lot, but they'll never be the most used things on any code base.
As a consequence, they shouldn't use very short names. They should let the 1-3 letter names available for local code. (But there are exceptions, of course. There always are.)
On the other hand their criticism contradicts their earlier point about widely used public/stdlib function names best having short names.