Ok, I see, but still production overflow from investments could just be erased. Just like when you use Great Engineer, when it would give more than you need to complete a wonder, he just gives the amount of production to complete a wonder, so no production overflow here.This is to avoid a human exploit. The excedent production after an investment was used for rushing settlers, allowing that cities to keep growing. AI was not able to do the same, so it was forbidden for hummies.