I am also a bit perplexed on the whole grease issue of filling the hub. However I believe with the design of the ez lube bearing system you must fill completely with grease for maintenance. The only other way(which some do) is to actually remove and re-pack the bearings. I would be cautious about not filling completely because there is no other way to ensure the bearings are getting it. There is no point in having the axle 2/3 full of grease if the actual bearings are running on old grease or worse dry...
2015 Eagle 324bhts
tv. 2012 F-150 s/c lariat ecoboost 3.73 max tow