GiveWell is like a test case for a centrally planned and managed economy; if they can accurately assess the return on investment and direct funding in the most socially profitable direction in a non-market driven way, then that demonstrates that at least some economic activities are amenable to this approach.
Disagree on the first sentence. Givewell’s planning is not substantially different from the planning executed by any ordinary firm, as the crucial distinction between a planned economy and market economy is use of force. Givewell has no guns, interest in using coercive force, or a democratic mandate, therefore it is not a prototype for a managed economy.
The distinction is perhaps more that more unprofitable organizations die and profitable organizations are rewarded. That’s the real magic. Property is defined by control and exclusion through force, that’s how it exists in the real world. Force was not actually removed, just moved a step back - the case with all law.