Moreover, I was not aware that the code might do something else than what one can know by reading the code and the public documentation. To be honest, if that was true, I would be disappointed, because I expected coreboot to be a possibility of getting away from private software and "you don't know what your machine does".
At the moment I believe that applying the patch does no harm. At least this is my current knowledge by running it at the MacBook2,1 for a couple of hours. Switching forth and back between coreboot versions (back to safe ones) works. I do not know if this was true for other boards.