The reason some people don't want to be labeled as part of the OSR is because the OSR is a reactionary mindset. Many of it's members get pissed off if you change something from 1975, or say ascending AC is an improvement over the old way. This is not true for many people, but enough bloggers and message board members push this view that I suspect it colors everyone outside the inner circles perception.
I know I'd be frustrated if I was making a game where I started with an OSR product, and then consciously added in the good stuff from 3e and had people saying that I was "betraying" the OSR. Heck, even suggesting that 3e added in good things to D&D is not even allowed on Dragonsfoot. 3e itself is referred to as "the edition that shall not be named". Talk about pompous bullshit. I'm glad that some publishers are moving away from straight clones of old games, and I hope more continue to do so. Hopefully, they will gain enough followers that the old grognards get shouted down when they start whining.