Unfortunately, that's the way it is. In your case, it would be easy to determine the true guilty if the existing data would only be evaluated correctly. The Sauber has certainly slowed much too late and was much too fast at this point of the route. That alone would suffice to recognize him as guilty. But such values are unfortunately not evaluated by the system. Probably because it lacks comparisons. If GTS had a good AI in singleplayer mode then these values could have been used for the penalty system as well. Then you could compare the values of the cars in the online race with those of the AI driver. Then, when accident occours and a driver decelerated more than e.g. 15% later than the AI brakes or is e.g. 15% faster than this is possible for the AI on this part of the track then this driver is to blame. With such and other algorithms PD could greatly improve the system. But that will not happen. Time would have been enough but so far we have seen no progress in this respect.