Hi, I researched the climb of the 777 some time ago.
A heavy plane leaving for a long haul will avg 2000fpm to FL300 and stay  there in the initial CRZ , as the plane is lighter it will step climb to a max of FL390. Boeing is showing a graph of weight versus CRZ alt.
If you dont like the Vnav climb then set your own climb
I step climb 2000f every 1 1/2 hr - works good.  ;D
the last step up must yield at least 20 min of CRZ to be worth it, says Boeing  :o

I agree that the climb should be corrected :(

Raymond     Boeing or nothing
KFLL