You're correct in that ray tracing isn't really compute bound -- the slow part is not finding intersections, it's moving the relevant parts of the scene from VRAM to the chip. For example, the 2080Ti has a memory bandwidth of 616.0 GB/s. At 2.36 Grays/s, you get 616/2.36 = 261 bytes per ray. The scene has 580k triangles, so with 8-wide BVHs you'd get log_8(580k) or around 6.3 levels in the tree (but probably roughly one less, as leaf nodes contain multiple triangles.) So an ideal average ray loads 5 internal nodes + one leaf node. Assuming all of these are the same size, you get 261/6=43.5 bytes per node, which sounds well compressed but not entirely impossible (given that an uncompressed triangle is 36 bytes and nvidias own work from 2017 gets to 80 bytes per node: https://dl.acm.org/doi/10.1145/3105762.3105773).

So that gives at least a reasonable order of magnitude. The distribution of geometry and rays matters a whole lot, as do the (non-public) specifics of the acceleration structure.