If I were you, I'd try to forget it as soon as I can, becouse it's wrong. 2.4 GHz is not in the water absortion band (I'd show you a nice graph, but I can't find one that goes to such low frequencies), a microwave would work as nicely in 1 GHz or 5 GHz, what matters is the H-O bonds, that are esentially electric dipoles and are excited when high-ish frequency and power hits them. You probably have noticed that fat heats much faster than wattr in the microwave oven, that is becouse is full of OH bonds, just as the GP is full of shit[1].
This is one of those moments when I wonder if most of the things I have learned in HN are bullshit, I'm usually struck with awe at the sapience of the HN hivemind too, but in times like this...
If you re-read my comment, you'll note that I only said that 2.4GHZ was in the 1-20 GHz band that is easily absorbed by water.
Engineers juggle multiple constraints, cost, size, power, and efficacy, and 2.4 GHZ choice was the result of the size of the magnetron that would be cost effective and physically fit into the oven. But it did, of course, have to be within the range of frequencies best absorbed by water, which 2.4GHz is, and which is why it's difficult to get bluetooth through your body.
Why don't you look at this link. I think it will prove your understanding is incomplete, and that water does have significant absorption in the microwave region of the spectrum.
