[marginalia_nu]

A nuance that is important here is that not all accesses are equal within the context of disk reads. B-trees are designed to minimize block reads, not memory operations.

I guess there are worst case scenarios with evenly spaced intersections spread out exactly one per block, but in terms of block reads it fundamentally doesn't matter how you intersect two such trees, you'll still have to read all blocks, and that is orders of magnitude slower than comparing the values within.

I think the tree structure can be considered cached in real world scenarios; not really relevant to the performance you'll get.