"Requires higher" may be a technically imperfect term (this
is the "tech" log forum after all)...
The 747-400 is "able" to maintain 250 at all weights at Flaps 1, but cannot do so at heavy weights with flaps up. We can legally accelerate to "clean" climb airspeed and retract the flaps below 10,000 feet under FAR 91.117(d) [and equivalent rules in other areas].