You'll notice most give you some information on how much they exceed (or not) a particular spec - for example - 79% better than IVA, or 20X better than IIIH etc.
I posted an article awhile back of an XOM engineer talking about specifications for the Supercar oil. They weren't trying to just meet the spec.
"We were trying to put together an oil that would just crush all of those tests and well exceed the limits for those, "Salvesen says
This.
"The spec", particularly for the API stuff, isn't "keep the engine clean" and wear-free, it establishes limits for the amount of wear permitted, the amount of build-up permitted...etc.
Yes, there are engines with mechanical issues that reveal themselves, and the limitations of budget-driven formulation (and approvals) early on. The OP mentioned a Toyota engine as an example of a "tolerant" design, so I think it's appropriate to mention the 2AZ-FE as one that isn't. The Saturn 1.9L and a few Audi engines also belong in this category.
Also worth mentioning is that nothing in any of the API, ILSAC, ACEA or OEM approvals mandates any sort of cleaning. None of the test protocols start with a pre-dirtied component and measure the degree of clean-up. Every one of them starts with a clean component and measures the amount of build-up against the permitted limit. This is a common point of confusion.
The ONLY major company that has developed any sort of "cleaning" test is Valvoline, with a modified version of an existing protocol, to measure the efficacy of the chemical used in Valvoline Restore and Protect against what is permitted to accrue in normal use as measured by the standard.
Short intervals are also not an inoculation against build-up. Sequence IIIH is only 90 hours, and run in a port-injected naturally aspirated engine that has no history of ring sticking or oil consumption. That's the equivalent of 1,800 miles at an average speed of 20 mph.
This is what a pass looks like: