It might not bode well for Darksun, Krynn, or any other much-differentiated setting, though.
Does it? WotC has a very different view of the settings than TSR did. Just looking at the setting since WotC took over...
Greyhawk (WotC) in 3e was turned into the "default" setting, introducing all of 3e's core assumptions like sorcerers.
Dragonlance (MWP) in 3e allowed all the core classes in the 3.5 PHB, plus all the races but half-orc and halfling.
Ravenloft (Arthaus) in 3e allowed all the core classes in the 3.x PHB plus all races but half-orc.
Dark Sun (Paizo) in 3e allowed all the core classes in the 3.5 PHB, all the psionic races and classes in the XPH, and all the PHB races but gnome and half-orc.
Dark Sun (WotC) in 4e allowed all the classes in PHB 1-3 (except for divine classes) and most of the races (save gnome, half-orc, and a few more that escape me.)
Even ignoring the obvious kitchen sinks like Forgotten Realms and Eberron, WotC has a pretty solid track record of allowing nearly all core classes and most races into a setting rather than strictly following only what was in the TSR versions. The days of setting re-writing classes or disallowing large swaths of the PHB ended when TSR filed bankruptcy in '97.
But I can't disagree with the assessment, it does make sense from the PoV of Brand Identity, for instance.
At the end of the day, that is something WotC has to worry about. WotC doesn't want to create a dozen clones of its own game to compete with each other like TSR did, they have been pretty consistent with keeping settings mostly using the same rules and only occasionally differing on lore or minor mechanics like races. It does homoginize the settings to a degree, but it also means the game remains familiar regardless if you are on a lightning, exploring a gothic castle, or surviving the silt sea.