Bro, you just talked about indexing a rotor on a hub.. I never even would have thought of that.. You without a doubt, have taught me something.That's the correct way to do it. However, checking the rotor after it is installed onto the vehicle is equally important. The rotors may need to be indexed to reduce the final LRO due to stacked tolerances.
This is why on-car brake lathes are a much more efficient solution. But at $20K/lathe, the privilege is limited to dealers or higher-end independent shops.