This is the upstream way of kernel building. The advantage is that upgrading to newer Buildroot versions is much easier than before. Also, writing new packages that build and install Linux kernel modules is easier. Finally, due to FBR_ADDITIONAL_KERNELS, it is possible to build other Linux kernel versions for testing.
Now, the linux-kernel-modules package is obsolete and has been removed. Use "fbr-make linux-modules" instead in order to build all Linux kernel modules.
pkg-generic.mk has been extended such it is now possible to group all Linux kernel patches per major version number and not per complete version number.