Well, I agree. I don't think it should be used as an overall measure, really. It has flaws, but it's certainly encapsulating of a few more factors than your usual measure does. For one, McGrath does great pretty much everywhere. So with that in mind, it does say something about him here, really, since he didn't do very well in one place and shocking in another for it to be distorted.
Let me clarify
. It is an overall measure, like for example career average, but it should never be the main criterion, like career average, because it can be distorted. But for most of the players mentioned, they generally had a very good record everywhere (Lillee, McGrath, Wasim, Marshall, Warne, etc) and it is still telling when you look at it overall.