You are correct, the surface finish is for appearance, although our manufacturer has expressed that the ceramic finish increases the durability in extreme harsh environment use (marine, etc).
Our manufacturer is an ISO9001 certified facility and among many other quality assurance processes, does random tensile testing during manufacturing to ensure material is consistent.
These fasteners are not a new concept, there are many titanium fasteners holding wheels on all sorts of cars; street, drag, road race, you name it. We are just finally making them accessible in the Lotus market. We have experience with alternative metals for wheel fastening and over the years have never experienced a single issue.
These should be torqued to 70-75 ft-lb.