In most of the world, a washer is just a means to evenly distribute the load when tightening a bolt. They are pretty generic.
On a Porsche, there are a surprising number of washers that have unique part numbers. When elbow deep and you see this in the parts book you often say to yourself “really? Come on. It’s just a washer!”. Wishing that any flat circular piece of metal would do, rather than wait for another parts shipment of washers that are $1.44 each.
Another example of Porsche specifying a special part, because it has a special purpose. The washer for the bolt that secures the rocker stand. It has a smaller OD (11mm x 17mm) than most M10 spring washers. This is so the bracket for the rocker shaft does not sit on the edge of it, and mate with the surface unevenly.
Also, the nuts to secure the rocker stand are thinner than your average 8mm nuts. If I had to guess, it’s to allow those studs to be short and get all of the nut threaded into position.
