People who do a UOA are looking at much more than wear metals, there is the matter of TBN, viscosity, and fuel dilution.
Just like the original poster, you are focused on one thing, and ignore important aspects of the topic, to make the short OCI argument.
If the TBN is strong, you’re not getting sludge - chemically, the alkalinity prevents sludge formation.
So, a UOA can absolutely help you determine the appropriate OCI for your engine, your use, and your oil.
Here is an engine that went 34,000 on the oil - and is spotless. No sludge.
https://bobistheoilguy.com/forums/t...-total-34-000-miles-on-hpl-hdeo-5w-20.377792/
Shall we ignore all other important, salient, factors, and put this example in the “short intervals cause sludge” category?
Because clearly, extreme interval cause super-clean engines.