I’m describing about how the term is used by EA folks, which may not match its formal definition. (“In practice, it can be used as. . .”)

> You can only throw up your hands and say "this isn't tractable" if tractability is 0, i.e. the charity doesn't help at all, no matter how much money you spend on it.

Even I don’t believe this. You’ve gone too far in the other direction and made tractability a useless metric.

If tractability could only be used to filter out literally intractable charities, it would indeed not be very useful. But you can also use it to compare different approaches and pick the best ones. Then you don't throw up your hands and say "this isn't tractable" but you throw up your hands and say "why are you wasting money on this when a much more tractable approach exists."