Try selling that to a client that keeps using the test against a site that is A rated everywhere else because Google's brand has fooled them into thinking a perfect score means better SEO.

Right, that would be an example of a "different problem."

I'd be hard pressed to let stupid things client/managers can do direct how this sort of tool should work. For example, it'd be silly to demand "score inflation" just because your client is unreasonable. Or rather, if a client is making your life hard, I don't think it's the world that needs to change.

What's your solution if your client measures your success by punching their website into https://www.worthofweb.com/calculator/? And doesn't take you seriously enough to listen to you in general?

This is a problem we run into, clients will run their site through a speed tester then give us a list of things to fix...without having a clue of what the ratings and results even mean.

True. This is like when movie studios start obsessing about the Metacritic ranking on their movies instead of focusing on the quality of the movies.