Sapped,
If you look at the article autotech references, you'll see that there are more steps of boost and the potential for higher turbo speeds when a single core is active. It seems Gigabyte implements this feature more aggressively based on the article you found on Tom's website.
I personally don't OC. I did once upon a time, but don't see the need given todays processing power, memory bandwidth and video performance. If I can get above 100FPS at high resolution and detail, I'm happy. I'm not telling you what speed to run your system at. The cores operate independently. You aren't going to see a dip because your application(s) is/are single threaded or only utilizes a single core. Credit to autotech for this info