That may be, I'm not familiar with the full body of what he's done, but just enough to be familiar with his style. But professional work isn't hitting a high note occasionally. Art is a competitive field, and professional work therefore requires being able to consistently output excellent work, and with an ease that allows it to be a financially rewarding use of time. As far as I'm aware, the only professional artist who does DF stuff is ......... and his art isn't really of the sort suitable to a tileset. Plus, he's presumably busy with his art career.
We have different definition of professional, a professional is anybody good enough to earn a wage getting hired to do a thing, the text book definition is "a person engaged or qualified in a profession." and both Meph and Mayday have been "Engaged" to produce art for a commercial product, they are therefore professional artists as far as I'm personally concerned, are they at the very top of their field probably not but that is just the nature of art, nobody can ever be the very best because of stylistic BS.
By that standard, there are even fewer professional artists since most art is lump sum or per-output and not wage-based. I don't think defining "professional" on the basis of the type of contract signed is meaningful for purposes of defining it (however loosely) as a quality or ability standard. While type of contract might make sense if you're writing tax policy, in practice I think who has or doesn't have that kind of gig is more based on networking ability and inclination than artistic ability. That being the case, I think being able to live off the money is a pretty solid (albeit somewhat variable, according to cost of living) metric for differentiating between a professional and a hobbyist that takes commissions.
I don't mean to belittle wither Meph or Mayday by saying this, but I'm not sure you understand the amount of knowledge on display in that game. The mastery of both palette and shading that's on display there is impossible to replicate without both training and practice, and not a tiny amount of either. Not only do I think it's beyond Meph and Mayday, but I think it's beyond anyone who hasn't spent years of their life with the primary aim of gaining skill in that style or in a similar style but in applications very nearly identical to that situation. Everyone who can do that is probably doing it for money right now, unless they've retired. Most games that make it to market don't have anywhere near that level of art, and it isn't because the idea of having better art never occurred to anyone on the dev team.
I got to be honest and just agree to disagree, But that is because I don't view professional art with same.... reverence you seem to, I'm not saying its not a skill as it definitely is a skill but it is not a skill that requires a degree to be considered a professional, unlike say a doctor or nuclear physicist where the degree is required.
At what point did I say "degree" or reference formal education at all? Doctors and nuclear physicists need formal qualifications to verify that they're as skilled as they say they are, because of the severity of the potential problems if they turn out not to be. Even then, you can do any research you can get funding for and publish in any journal regardless of your qualifications, if the research is good enough. But that's beside the point. No matter what populist view you take on it, the art you posted as an example showcases a lot of skill. Nobody has that skill who has not acquired that skill, and although talent can mitigate this, at the end of the day gaining skill always requires time spent learning. There's no "reverence" there, that's just how it works.
This would be less representative, and wouldn't look as good as your example game or necessarily better than what Mike&Meph are planning now anyway.
I personally think it would be more representative as its showing you more info at the same time,
That's not what representative means. Because what it shows you bears less relation to the actual situation (the trees don't lean north along the ground, but go up to the next z-level) it is less representative; it does not represent the "reality" of what happens in the game engine. Unless the game were converted to full isometric, it basically has to be top-down to not be confusing, games that use the method you describe have to have everything carefully constructed and make exceptions in all the right places where they won't be noticed. Otherwise you'll have tons of situations where you can't see what's going on because it's behind a tree or castle or mountain. Of course, most people's idea would be "like Stonesense but in the game" but the degree of rework would be substantial and might also necessitate functionality changes.
In short, there's a limit to what's reasonable to expect.