I think it's not only the awesome high ISO performance here but also the balance of noise, color, gradation etc.
There is "ugly" noise (mostly) and there is "nice" noise (sometimes). The H40 (in conjunction with Phocus) apparently produces a look with "nice" noise (at least to me). This goes also for the ISO1600 portrait posted on LL a while ago.
It's hard to explain and maybe nothing you can describe in technical terms (at least I can't)... for instance I am finding the noise of the P21+ "nice" whilst I don't really like the noise of the P45 (though they have basically a very similar same sensor design). I also like the noise of the M8 whilst I have yet to see "nice" noise of an CMOS sensor.
Probably it's very personal. Anyway... this ISO800 simply looks great.