The Wydendorf kit is designed on the principle that the original bores have the correct angles since the reamer guides itself into the existing holes.
When I removed my camshaft following a broken tappet, I was able to see that the trace of the roller is well centered and has the same width on all the cams which means that the bores are indeed perpendicular to the axis of the camshaft. In addition, the rollers are not cylindrical but slightly spherical, which compensates for small defects in perpendicularity.
On the other hand I have not checked the maximum opening angle of the valves of all the cylinders and I can therefore not affirm that the bores all have the correct angle in relation to the axis of the cylinders.