> which purports to gauge a study's rigorousness as a simple percentage

That's not what it does.

Some of the studies showed a causal relationship clearly. Some showed merely an association with a plausible argument about why it was mostly causal. You can decide what proportion of the unproven effects to include.

In reality, there's more causal effects than those that are proven, but not all of these measured associations are causal.

It's just trying to visualize bang for buck. Not science, much less pseudoscience.

EA ended up getting coopted by people who weren't interested in altruism at all but that doesn't seem like this.