Also, regarding your specific situation, with the stones hitting the edge on the heel, and not at the belly or tip, it is because it is common practice when hand sharpening (on stones or power tools), to rotate the knife up at the tip to create an even bevel width visually and dimensionally, but the angle has changed, most time because of the taper of the main grind, and the curve up to the tip, but on controlled angle systems the tip bevel is almost always a little wider than the heel bevel. Just physics – can’t change it, unless you hand sharpen. I have also heard that the change in angle was to strengthen the tip by making the angle wider and having more material behind the weakest part of the knife.
