Magnetrons are a completely different animal and it depends on how you determine or measure efficiency.
There's really only one way to honestly measure efficiency. Energy (Watt-hours) going in vs temp increase of volume of water (btus for example) coming out. All units for energy are more or less interchangeable (joules etc) so it is very easy to come up with a percentage that you can use to compare to any other heating technology directly. Or you could simplify to dollars in vs amount of hot water out. That said I absolutely agree they will most likely try to turn this into something convoluted and try to paint it in a way that makes it look better than it is. But there could be genuine claims in there, such as getting hot much faster, wasting less heat in a hot element once water is switched off and so on. So overall it could genuinely be the best available thing out there as far as dollars spent per year over the life of the product. If that's the case it won't be better by much but in a market so huge (several markets really) it may be more than enough. As far as manufacturing by Christmas, no way, we'll be lucky if we have all the figures regarding efficiency and costs by then.