Well, the title might be misleading, but it’s true for a few niche cases at least.
So I don’t know when they fixed this, but thanks to a comment on /r/hackintosh, I took a loot at clover automatic c-state/p-state generation for the first time in a year, and it seems to be fixed, at least for Haswell on Yosemite using XCPM. I’ve been running my system without an SSDT for a few days now, and can verify that speed-step, sleep, etc. are all still working great.
Why should you care? Well, it means you don’t need to worry about generating an SSDT or configuring drop-tables anymore to get native speed-step using XCPM mode with Yosemite. This also means that overclocking should be more user-friendly now if you use Clover; just adjust your max turbo speed in the bios, and clover should update automatically, no more generating a new SSDT for every clock-speed bump/test. You will still see a P-State Table MisMatch message in your system log, but in my quick testing, the overclock works fine.
Of course, if you’re using an SSDT for anything other than power management, this is all moot; keep using your SSDT.