the ballast is designed to run super
they are not designed to not have enough current to reach proper reisistance levels with a bulb not designed to run at that amperage
your ballast to run that bulb at 400 , the ballast runing the circuit with the wrong bulb at the end of it will have be working to try and meet the resistance it is set up for, thats why digital ballst have dimmable seetting with wattage numbers on em, they are designed to do it, not run to little voltage to a bulb trying to pull 400 w instead of 250 and will over load your ballast,
YOU HAVE ZERO EXPERTISE WITH ELECTRICAL CIRCUITS, STOP GIVING ADVISE, and the avg person will know even less then you ,sound advise is correct advise, at least with electrical circuits
do yourself a favor and google MMJ electrical fires and i bet those people thought what they were doing was good advise too