I would ask 'where is the benefit?' in that at very high speeds there might be a benefit in friction losses but at low speeds they are arguably so small that they are not really worth worrying about in the same way. Possibly there is more lost in the seals (if they are properly wetted with lube) than in the bearings anyway. Also in reality a lot depends on how stable the thickener is, if you are reliant upon that for the low speed film thickness. Plenty of greases start to degrade by the thickener changing first of all. Unfortunately bicycle parts see some pretty horrible conditions and they don't always have perfectly smooth surfaces in the bearings either.
So a grease that works great in a lab test might not work so well in the real world. Ideally you would want to have
- super anti-corrosion additives (clue; the grease is recommended for 'open' bearings and/or gears in mucky conditions)
- grease fluid enough that it keeps seal lips wetted (so the seals can work as intended) but not so fluid that the lube just runs out of the hub (*)
- grease that shears in a particular way so that it doesn't 'ball up' in seals (*)
- EP additives and/or solid lubricants to inhibit wear at the very lowest speeds (they don't even measure at bearing speeds that correspond to climbing in bottom gear)
- a thickener system that isn't destabilised by water, road salt, small amounts of rust, or typical soil chemistries, even under long term exposure.
- a thickener system that works differently under different conditions (**)
(*) the NLGI consistency is rather a blunt tool in relation to what you really need in a bike part. The NLGI test basically measures how easily the grease shears at a certain speed under a drop weight test, i.e. the distance the grease is penetrated is measured. The grease sample is 'freshly worked'; you would get a completely different result if the grease is left for different lengths of time. Nearly all commercial greases 'shear thin' so a small change in viscosity at high speeds affects the test score greatly whereas a large change in the low speed viscosity has a relatively small effect on the test score, even if it profoundly influences the way the grease will work in a bike part.
I've concocted lubes which when sheared, are little more draggy than plain oil is, yet stop flowing under their own weight within fifteen seconds of not being actively worked; to my mind this makes for a pretty good bike hub lube to use in sealed hubs because the lube will keep the seals wetted and coat all the parts inside a hub nicely, but won't allow excessive amounts of leakage to occur when the bike is not in use. In an unsealed hub you would want something thicker than that.
(**) in an unsealed hub especially, how the grease is pushed around by the ball bearings is important. Some greases use additives that tackify the grease and/or make it 'stringy'. In low speed bearings this can help to keep parts coated under conditions that would just push other greases aside.
So the bottom line is that you usually can't just choose a grease meant for another application entirely on the basis of test scores meant for that application; basically you need to do some tests to show that it isn't going to fail (usually in some terribly prosaic fashion) when you start using it on bike parts.