Yes, that is assumed, but unless I am mistaken one does need to run a circuit that is able to handle the largest load that could be put on the unit.
In your example, I would assume it is possible, but consider that even using fast switching, in order to get the water that had the first temp increase over to the next cavity for its second heat bump the water has to be flowing. So that means water flows into the first cavity in order to get the water with the first bump to the second. So, which is going to be powered ? The second cavity in order to give that water its second temp bump ? or the water now in the first cavity that has not yet had a temp bump ? The question scale into more muddled territory when one tracks the water to and through the third and fourth temp bump.
So, for sake of discussion, let us assume that it is possible, that the fast switching can be such that only one magnetron is on a any moment, and each cavity-full of water gets four temp bumps as it moves through the four cavities.
If that is the case, then at most there is in effect 1 magnetron on all the time ("at most", maybe less if each temp bump can be delivered fast enough). So at most 1500 watts is being used, and that nicely fits into a regular 110 plug-in (assuming the energy expense to bump the voltage up to the kilovolt range needed to drive the magnetrons can be ignored).
So, at most, 1500 watts would be used, which also means that, at most, 1500 watts could be absorbing at heat into the water. That gets us back to physics 101 that we went through here ages ago showing the very small volume of water that could get sufficient temperature increase per time, or viewed alternatively the very low temperature increase that could be delivered in a sufficient flow of water. This same physics 101 lesson is what is behind the change from the single cavity to the multicavity.
Seems like a catch-22, with the only way out being having the multiple magnetrons working together to deliver more heat per time into the water, drawing more electricity in doing so.
So, for sake of discussion, seems like we need to see the numbers, as has been said so often here. The temp-rise per rate of water delivery per minute via municipal pressure, and the electric consumption needed to accomplish that. Once that info is on the table we have a chance of derisking this, or at least setting out strategy, speculate on flip gains or also build a core for longer-term investing. At present as I have said, I am betting on the longer-term success or failure of this will rest on two things: total cost of ownership over lifecycle, and niche markets.
