On the one hand, I can agree with Mearls. Why do we obsess over the specific rules of our edition? People who played football talk about how they played football, and don't scream "YOU PLAYED WITHOUT TWO POINT CONVERSIONS YOU ARE THE ANTICHRIST." "YOU YOUNG PUPS THAT PLAY WITH HELMETS AND PADS ARE WUSSES." Concentrate on the shared experience and let people do it the way they like.
On the other hand, there's a really, really good chance that this is apologetics for what they are about to do to D&D, which will transform it away from what even 4e players recognize as an RPG, and plead "but aren't we a big tent CAN'T WE ALL JUST GET ALONG." "This is the current incarnation of the D&D BRAND, you can experience it in, you know, other ways if you like, DON'T HIT ME IT'S NOT MY FAULT HASBRO MADE ME."