It’s the static-typing, not the low-level-ness, doing most of the heavy lifting in making code JITable/WPOable. You don’t need to manually inline a comparison function, if the JIT knows how to inline the larger class of thing that a comparison function happens to fall into, and if the code is amenable to that particular WPO transformation.

I would compare this to SQL: you don’t optimize a SQL query plan by dropping to some lower level where you directly do the query planner’s job for it. Instead, you just add information to the shape of your query such that it becomes amenable to the optimization the query planner knows how to do. That will almost always get you 100% of the wins it’s possible to get on the given query engine anyway, such that there’d be nothing to gain by writing a query plan yourself.