OK, lets try a thought experiment. Assume that temp/wind/etc is constant everywhere at 330 and constant everywhere at 350.
Lets say that in order to be able to climb to 350, you have to burn down to 200,000 lb of fuel *.
Now lets say that if you go to LRC, you burn down to 200,000 lb 100 miles sooner than you would have otherwise.
Now lets say that to climb from 330 to 350 burns 10,000 lb of fuel (same disclaimer about number applies)
So, either way, you arrive at 350 with 190,000 lb of fuel.
So, which do you think saves fuel: arriving at 350 with 190K lb of fuel 100 miles sooner, or arriving at 350 with 190K lb of fuel 100 miles later? In which scenario will you land with more fuel, all else being equal?
* I have never flown a 747-400 and have no idea what the fuel loads and burns are so I'm just picking numbers at random. If you don't like the numbers substitute in ones you do like. The principle remains the same.