> Some of their previous grants are downright laughable, like spending $30K to distribute copies of rationalist Harry Potter fanfiction (Harry Potter and the Methods of Rationality) despite the fact that it's freely available online. (Source: https://forum.effectivealtruism.org/posts/CJJDwgyqT4gXktq6g/... Ctrl+F "Harry Potter")
They're not allowed to make money from this Harry Potter fan-fiction IIRC, which this is (one that teaches effective altruism concepts and rationality), so I don't see how this would be a way to launder money.
It's also worth noting that this was 28k out of 923k USD, so not a too big part of it (~2%). Of course the money should be used for other things if it's estimated to be more effective though.
The reasoning is in the post you linked which I think gives a pretty good explanation. They're given to 650 math medalists (so ~43 USD/person) which they deemed to have good target audience for this.
Is this how money is laundered in non profits?