Here is a closer look of 'contact'...

the actual point of contact between the lobe and the shim/tappet is just about where the shadow's edge is. [such a lucky outcome is just that: luck. I am just an amateur photographer. It wasn't until after I took the pic, and was editing the pics, that I realized that the shadow was being helpful.]

At this point of contact, the actual contact area is very narrow. It would look like a line drawn between the lobe and the shim, being the length of the lobe's width.

Another aspect of this point of contact is that it is directly below the centerline of the camshaft axis...in the middle of the shim/tappet.