Flintstone, FAR 25-1001 (?) Fuel Jettison System, states that an aircraft must be able to satisfy the approach climb, landing climb criteria within 15 minutes of takeoff. With or without a fuel jettison system.
If an aircraft can satisfy the requirements without the fuel jettison system, it wont be installed, e.g. B737.
In some cases the fuel jettison system becomes an airline selectable option, e.g A330.
So it reasonable to get two different answers that will actually be correct as they will apply to the same model of aircraft but different certification requirements or purchased options.
Mutt