I suppose it’s a question of whether you count “documentation” as engineering.
It is elegantly complex and featureful. And (sometimes intentionally) poorly documented, as much of that implementation is seen as “an implementation detail”.
Especially when it comes to API's, documentation is 100% part of the engineering. Very few non-trivial API's are self-explanatory because you have to map a complex problem space to an imperfect engineering-focused formulation of the problem domain, and the mapping usually involves introducing design patterns to make the problem space easier to manage in code.
It is elegantly complex and featureful. And (sometimes intentionally) poorly documented, as much of that implementation is seen as “an implementation detail”.