I don't think it makes sense, because the maximum penalty due to the tranitions is fairly low (~30 us out of 650 us, and only under pretty much a malicious load

I don't think it makes sense, because the maximum penalty due to the tranitions is fairly low (~30 us out of 650 us, and only under pretty much a malicious load that transitions at exactly the right points), and mostly you want the higher frequencies when you can get them: they quickly overwhelm the small transition periods. Also, someone indicated to me in private correspondence that even when the frequencies are manually set so no transition takes place, the throttling periods may still take place (which makes sense since the required voltage may still be higher).