There was a time around 2012 or 2013. 12951 would run with an extra coach on most days, leading to wrong outcomes for everyone who would predict WL/RAC. Such instances of extra coaches, down gradations, and several other unknown factors have affected the accuracy of everyone over the years. The only way out is not to think too much about it. It's all trial and error. The more you predict, the better you will get at it. Of course, I do believe predicting PNRs whose outcome is solely dependent on HO availability doesn't make sense. You may see the overall accuracy as 85%, 83%, or 80% today for some. However, in the beginning, it was only around 60-65%.