We’re talking about direct computations. Someone with a massive memory of pi has it memorized, they aren’t computing it via an infinite series in the moment.

The point being made is that it’s much more efficient, both in time and energy, in having the actual computation done by a dedicated and optimized program that only takes a few CPU instructions, rather than trying to approximate it using the giant neural network mind that is a LLM. And this is similar to humans, our brains burn way more energy multiplying large numbers in our head than a CPU would in the few nanoseconds it would take.