The thing is anyone actually having a dedicated machine to run that (old style) RT process is almost surely running on an SMP machine and has isolated his CPU from hardware interrupts and other processes. But even doing that, the kernel thinks that IT owns the CPUs in your box, not you, and requires some time on YOUR cpu regardless of your requirements. Folks, the kernel is just plain broken when you have 4 processors and cannot dedicate %100 of a single processor for a RT application. When you run a process at %100 on a single processor it breaks the kernel because the kernel can't get the processor for it's workque and other crap it thinks it needs to run on YOUR cpu. I think all this throttling crap is more of a "Lets not let userland break our kernel" sort of thing rather than "Lets not let user land break them selves" sort of thing.
I will admit though, for a non SMP box this is probably a good thing as a default setting.