Lapping scope rings so they perfectly fit the scope's tube has been going on in the benchrest world for many years. It's done so the scope tube won't bend as both rings probably don't have their exact center relative to the ring diameters aligned with each other after they're mounted on the receiver. Lapping them makes the inside of each ring on the same axis. Tightening lapped rings will not bend the scope tube.
Most rings, when attached to bases, do bend scope tubes a little bit. Most folks won't notice any problem. Errors are typically no more than 1/4th MOA, but may be bigger depending on how much the scope's main tube is bent.
Some scopes, typically those with aluminum tubes, when bent even the slightest amount, will bind their adjustment mechanics. Which means the adjustments (E and W) are no longer repeatable nor accurate. Therefore, it's important with some scopes that they not be bent in mounting. Lapping the rings prevents this.
Arnold Jewell (trigger maker) now has a set of rings with live centers in them. These centers float and automatically align with the scope tube. A really neat and simple system. They are not cheap, nor even medium priced. But they do work great.