The "learning system" is somewhat a confusing statement. It really has nothing to do with intelligence.
Sure, they "learn" a better driving line. However, if they are not prone to the same behavioral mistakes a human is, they are nothing but an image which becomes more and more "in focus" until the picture is so clear there is no getting better. I don't know how anyone can call that "intelligence".
True intelligence is the ability to form a solution given a problem with a known set of variables and a set of unknowns (like "is that driver gonna go wide or not"). The "learning system" as I have seen it is nothing like that at all.
The reason the AI are so bad revolves around the learning process. We have all seen what happens as they learn and fuel decreases... only to fill them with a full tank and watch them spin in circles....
Hardly Intelligence.
It isn't completely useless though. I would say it would make a good component IF it reset to a default value at the beginning of each first practice session. So learning resembles going away and then coming back to a track. The default value should represent a skill level of the driving AI. The learning process should be done before hand (by the devs) and contain a set of different degrees of knowledge and behavior which can be assigned randomly to different driving AI at the beginning. The degree of learning should be random also.
Of course we still need the other 90% of the AI.