A lot of altruism is quite literally wasteful and ineffective, in which case it's pretty hard to call it altruism.

> they could have been 13% more effective

If you think the difference between ineffective and effective altruism is a 13% spread, I fear you have not looked deeply enough into either standard altruistic endeavors nor EA enough to have an informed opinion.

The gaps are actually astonishingly large and trivial to capitalize on (i.e. difference between clicking one Donate Here button versus a different Donate Here button).

The sheer scale of the spread is the impetus behind the entire train of thought.