How to reliably tell if the rim is correctly drilled?
It looks like the holes are quite close to centerline of the rim, but the rim profile has an angle that can be used as reference. So, here are my suggestions:


Use a vernier caliper to measure the distance from eyelet to the angle. Measure both to both sides, and several eyelets.
Arrange lights so that the flat center part is highlighted, like in the photo but so that the highlight covers several eyelets. Take a photo, zoom in and count the pixels to both edges of the highlighted area.


Finally, when you know how the spoke holes are arranged, you can always build the wheel so that the spokes are not crossed over the valve. Just start at the valve and choose the side for first leading spoke so that they match the rim, or choose the side first and spoke hole that matches the side second. Note that spokes from the same side are two holes apart, and you need to have spokes from both sides not cross at the valve.