I don't think HxH is a good example after Togashi did in the chimera ants arc, also, sometimes Togashi does a narrative that's actually confusing, the ones that think that "wow, that's deep" are just a bunch of deluded guys, and I don't need a author needs to write a bible to shows that he's writing a "difficult manga", see Eat-Man and Desert Punk for example, a simple setup that's easy to understand, but with a complex storyline, or in the case of Karakuri Circus and Steel Ball Run, when sometimes the story is hard to follow, it's still enjoyable, and you don't need a 200 IQ to understand it. In my personal opinion, that's what I consider as a "difficult manga", but honestly I don't understand what Kurumi, or the both authors, trying to implying here.
I know that "difficult entertainment" is not for everyone (because of how confusing it can be for people who are not used to "something new", or how complex it can be, or money issues), but the way Ahko and Kurumi said this is ambiguous.