Having the shims located on top of the bucket is nothing new. The early Z1 Kawasakis (73-80) had the shims located on top of the bucket and the camshaft rode against the shim. There is a tool that would hold the valve down so the shim could be replaced with one of the correct thickness.
The design is similar to what KTM uses on the 690 motors and 9xx motors. 10mm bucket shims.