He means that the headers are precompiled for 10.2 instead of 10.3. Which is a somewhat arbitrary decision since CW supports 10.2 and 10.3 as the development environment. It's really not a big deal since it's trivial to recompile all of your libraries and precomps. I suppose they could just ship several precomps made on a bunch of different versions of the OS (i.e. by using the SDKs) but that's not really something I need.