I'd argue that intelligence has a contextual nature as well. A simple example would be a computer chess tournament with a fixed algorithm that used as much resources as you threw at it. Say you manage to increase the resources for your team steadily by 10 MIPs per year, you will not win more chess games if another team is expanding their capabilities by 20 MIPs per year.

If you're comparing a randomly selected intelligent system against another randomly selected intelligent system drawn from the same pool, then of course the relative difference isn't going to change as you crank up the general level of intelligence.

But if you compare one of these against anything else as you crank up the general level of intelligence then it's a whole other story. And these other comparisions are pretty much what's at stake here.