That paper is pretty good but it's comparing bw-tree with much simpler in memory data structures. I think bw-tress might work specially well for fast-disk storage.
This was my interpretation as well. I'm going to compare a disk-backed bwtree with a disk-backed ART, both backed by the same pagecache, and maybe end up with an ART that scatters partial pages on disk, bwtree style. But I need to measure apples to apples on the metrics that matter for storage first. The pagecache is where most of the complexity is in my implementation, and it makes building different kinds of persistent structures on top of it pretty easy. docs.rs/pagecache