As this person seems very worried about counterfactuals, I should probably point out that the All Grants Fund does still make substantial grants to the Top Charities because they don’t get enough granting opportunities that are reliably estimated as more effective than a top charity, so on the margin your donations are equivalent.
This may change in future—GiveWell are investigating lots more scalable grants in things like water treatment and humanitarian contexts.
As this person seems very worried about counterfactuals, I should probably point out that the All Grants Fund does still make substantial grants to the Top Charities because they don’t get enough granting opportunities that are reliably estimated as more effective than a top charity, so on the margin your donations are equivalent.
This may change in future—GiveWell are investigating lots more scalable grants in things like water treatment and humanitarian contexts.