The main problem I see with this is that it seems to implicitly assume the Extended Church-Turing Thesis, which is widely suspected to be false (assuming that quantum computers can be built, and that BQP is not equal to BPP).

How would a superintelligence living inside a cellular automaton (like the game of life) ever hope to estimate the probability of intelligent life arising in a world where chemistry is governed by quantum physics? How could we ever hope to understand the values of a typical superintelligence built in an alternate universe filled with Popescu-Rohrlich boxes (https://en.wikipedia.org/wiki/Quantum_nonlocality#Superquant...), let alone engage in acausal trade with it?