The OP seems to be confusing the concept of API and library layering with the idea that something is something else.
To be clear: in software almost everything is built on top of other things using libraries. This doesn't mean the new thing that is built is that thing at all, and indeed that new thing may be able to switch out the lower level library for a different implementation.
To be clear: in software almost everything is built on top of other things using libraries. This doesn't mean the new thing that is built is that thing at all, and indeed that new thing may be able to switch out the lower level library for a different implementation.