I've used the same funds for an ISA and a pension illustration. The growth rate for the ISA is 5.00%. After the 2% inflation adjustment, why is the pension growth rate 2.94%, not 3.00%?

This is because the pension illustration uses a compound interest calculation to derive the growth rate after inflation, (1 + unadjusted growth rate)/ (1 + inflation) = (1 + adjusted growth rate).