They are trying to prove a point.
If it had happened in say the 3rd race of the season and the two cars were both excluded then the drivers would both lose the points. why should it be different now?
The FIA have made a rod for thier own back, they started the war and McLaren are now seeking clarfication.
Whatever the outcome, should a car be found to be outside the rules next year then the FIA will find it very hard to deduct points if they don't this time.
I think this years title is so tainted it should be null and void anyway, Ferrari got away with running a dodgey car in the first race, if that had been dealt with properly at the time I doubt we would be at the point we are now.