We can see that in both sets of experiments, the precision and F1 score on the unchanged known classes (comp.windows.x and rec.motorcycles) are better when a more similar class (closer in distance) is selected in training.
comp.windows.x achieves the best result when comp.os.ms-windows.misc is the second known class, and rec.motorcycles achieves the best result when rec.autos is the second known class.