I have installed several sinks in granite, and had a couple installed for me. I also have never used the 2 cm granite, only 3 cm (1-1/4 inch), which is a pretty common thickness. In all cases, the granite was drilled by a granite shop, and threaded inserts were epoxied in place. The drill holes were templated off the actual sink to be installed. Special stainless steel clamps hold the sink in place, and the clamps are held in by stainless steel bolts that use the threaded inserts.
I have read several posts indicating that 2 cm granite is too thin to accept threaded inserts, and requires a plywood subbase to attach the sink to. Nothing suggesting an install such as what you have, but perhaps the technique you showed is acceptable based on local practice.