I can't make sense of that. Care to rephrase? Efficiency? It'll be about 100.00%, I expect. The interface is designed for a LOT more stress than it will receive. You just can't pull/push as hard at it as a disc brake can. I mean, can you accelerate from 0 to 20 mph as fast as you can stop from 30 to 0? Not even 300HP cars can. so the hub won't twist or some such. Disc brakes are brutal mo-fo's. If it stands up to one, I'm golden.

As to reliability, if I drill the cog right and tighten down the bolts properly, it will be bombproof. Trust me, it will be around with the cockroaches after WW4. The spaced-out axle is the only weak point, but it's not too bad at all. The side-to-side stiffness and spoke life of the wheel will be superior to derailer wheels by a long way, cuz it will have close to zero dish.

The problem with regular track hubs is that they suck. The threaded interface with the lockring is just crap. If you don't take care of it, it strips. If any of the 3 threaded parts is not good quality, it will still strip even if you yourself don't mess up. Also, they aren't cheap, and they are not available here. Only Miche is (maybe), They are also heavy with those silly high flanges. Plus the chainline on track hubs and the spacing are not exactly flexible. I have a 130 frame but may go to a 120. The Miche can handle this, but it still has a 42 chainline, which won't change unless you respace and redish. With the bolt-on system, I just slap on a wide-foot SS cassette cog if I need a wider chainline. Also, I prefer the look and the whole home-made vibe. A good couple of people have done this, all with success. Plus, on a track hub you need special tools to swap cogs. With bolt-on, your multitool is easily enough.
The Miche hub costs $56 here, three times the price of this Shimano (Local prices, both new from a shop.) That means that I get a stronger, lighter, more flexible and more unique hub setup and money left over for butted spokes instead of straight, plus money for the rim. Who wants a track hub???