Oh, sorry, made one more attemp and now I see your algorithm differently.
So you propose to use oE and oV as a markers of borders for what I call Realm.
But there may be very little significant bits in one of this ranges.
pg_sphere and PostGiS extensions tried to use 1 as a marker, with
alike formula. And that generated not a good tree.
Here's how they done it
https://github.com/postgis/postgis/commit/9569e898078eeac8928891e8019ede2cbf27d06f
I'll try to compose a patch for your formula later, I think we should
just try and see, it is easier than to reason about digital floating
points.
Best regards, Andrey Borodin, Octonica & Ural Federal University.