Some people would put oil in their hub and bottom brackets bearings to save a watt or two on race day, so I don't see the problem with trying a thinner grease. You'll probably just have to replace it sooner.
Also, some hub manufactures -- Chris King, DT Swiss, others -- specify a certain type of grease for their ratchets or ring drive systems.
As far as I can tell, Phil or Park greases are just common greases with a little rust inhibitor, but arguments that some lubricants perform a given task better than others seem valid, not totally marketing BS. Some grease hardens over time, etc. S & S Couplings did a test for thread galling, and endorsed a teflon based grease based on a specific test where they basically pinched a nut and ran a bolt through it again and again until it broke.