Because 1 & 4 tanks are small tanks (only hold about 30,000lbs) and if 1 &/or #4 x-feeds fail closed you are truly going to have to maybe dump fuel and land since there is no way to get fuel to 1 & 4 engines without using the x-feeds. So you always takeoff with these valves open and leave them open until 2 & 3 are equal.
So whats your point?