That's for sure, there is no correlation between use and viability (you only have to see Volcarona, Hoopa and Gliscor are very high in VR but very low in use). But I still maintain that a rank D does not cost anything (the example of Uber is very simple: there is Deoxys-N or Arceus-Bug). It would contain anyway that the seven BL that I mentioned above (no need to complicate and therefore to know whether to integrate mons of UU or lower)
For starters, Uber is not usage-based, so unused (and unviable) Ubers are still going to be Uber, so they have to be in the ranking even if there's no reason to use them.
BL Pokemon are not going to be in the OU viability ranking if they are not viable because they are not OU, just BL.
Contrast with the likes of Vaporeon in ORAS UU that was in the viability ranking despite being completely unviable because it was still UU.