It has nothing to do with EI. If you dose CO2 the additions of CO2 due to water changes are not significant. If you don't dose CO2 the CO2 additions due to water changes cause a fluctuating amount of CO2 in the water, leading to algae. If you want to fertilize by the EI method for a no CO2 tank, first the doses have to be much smaller, since the plants don't grow very fast, and don't need the additional fertilizers. Then, any water changes have to be few and far between, which isn't a problem because you are dosing so little of any fertilizer anyway.