That's one way to read it. But another way to read it would be as follows:
I want to see some pictures where that party of two both happen to be male (or female). Or where the entire party belongs to the same ethnic group. In short, I want to see art that is just art, and not some sort of attempt at political correctness.
I mean, doesn't it seem just a little insulting to have every cover consist of two adventurers, one male, one female? Why can't there be pictures of all-male (or female) adventuring groups? I know I wouldn't be offended. And I'd love to see some classic "rescue the damsel" pictures out there.
And it'd be great to see an all-african adventuring group. Or all-celtic. Or all whatever. It'd make the stories seem more "real world" as opposed to a fantasy version of the modern day.
Again, my two cents. And this really has nothing to do, on the whole, with Dark Sun. Let's just say that I rarely like wotc art decisions.
There's a number of problems with this, however. First, and most obvious, is that there's a huge population of younger generation gamers who find the whole "damsel in distress" trope cliched at best and demeaning at worst. Nothing screams bad, decades-old alpha-male fantasy like a bunch of a strong manly-like dudes rescuing a beautiful (and often scantily clad) female from a horrible ugly monster. There's a reason Hackmaster covers poke fun of this trope all the time. Also see Shrek.
As for the homogeneous groups idea; well that goes against several principles WotC is working from. From a pure aesthetic perspective, few things are more bland than a group of similar-looking people. Like it or not, diversity (and I mean in the general sense, not just the huggy-PC sense) is more visually interesting (at least, it is to a much broader subset of humanity). Secondly, having a homogeneous party on a book cover sense the opposite message to players: parties need to be diverse and have a great deal of versatility.
Adventuring parties are
special. This is reinforced by the source material time and time again. What you call realism is indeed realistic... for everyone in the world
save the heroes. Thus, most traveling groups in any D&D world will be quite homogeneous; a group of Elven scouts, dwarven warriors from a single clan, a band of human knights, etc. But PC groups are supposed to be different... the basic idea that the PC group will succeed where the above NPC groups failed is because they are diverse; because they bring so many different complimentary things to the table. This has nothing to do with political correctness and everything to do with a) good principles of artistic design and b) reinforcing these important ideas about party makeup.
I'm not saying I'm a huge fan of WotC's art... my favorite art was always from either the 3.5 Eberron books or the third party 3.0 Ravenloft books. The problem with 4e art as a whole is that while it is certainly colorful, it completely lacks
action (especially the covers).
Edit: Oh yeah, and the psionic halos are stupid too, but this only reinforces my point... you visually distinguish your psionic characters not by giving them a stupid halo but by showing them
doing something psionic. If you draw a dude, and there's all sorts of crap floating around him, okay, he's a psion. I get it. Somebody's punching a goblin in the face? Yeah, that's a monk.