And you also should not render so clean images. Sure it's good to test how the new image filter contributes to final quality image, but it will be harder for human eye to spot the differences. I'd do one more test, again with the same amount of passes, but lower amount of them (let's say a half) so you can spot the differences better.
From the current test, it appears that the HQ image filter mainly helps to resolve very small highlights/glints.
I get what you are saying, but to me practically, the noise in both of these images (HQ and non-HQ) are the minimum amount of noise I'd be willing to accept in my renders. There isn't any reason for me to make comparisons with more noise/less passes, since I'd never use them any way. My tests are more practical for me to figure out if this feature would benefit me.
Maybe other people can focus more on the academic, less passes/more noise tests.
This yes, wanted to mention that too about the logic in testing on final quality renders. It is like we are aiming for final quality in the end right? So that is what we should be comparing.
Just was to sleepy yesterday.