V6 TDI Camshafts: Performance & Replacement

Hi,

It was just a topic of discussion in another thread, and it's quite embarrassing for modern engines, the camshaft failures that occur in V6 TDI models.
The problem affects not only the well-known AFB, but also the newer AKN engine. With mileage exceeding 100,000 km, the camshafts wear out, and eventually, so do the rocker arms. As a solution, it is recommended to install specially hardened valve lifters.

However, I'm unsure about the actual cause.

-Material: A few years ago, Audi ran an advertisement in the VDI Nachrichten magazine featuring their NW products: The material used was "Ledeburit," advertised as "indestructible." Ledeburit forms in eutectic gray cast iron during rapid cooling. Using appropriate casting methods (e.g., shell molding), a hard layer of Ledeburit is created in the outer regions, while the core remains soft but tough.
Has the quality of the Audis not always been quite satisfactory? Are soft surfboards still available for purchase alongside the more rigid ones?

- Lubrication: With sufficient lubrication, the camshaft and rocker arms are separated by an oil film, which means that it doesn't matter whether the material is particularly hard or soft. Is there a lack of oil here, or could damage (e.g., PD damage) be prevented by using a suitable oil?

-Geometry: Do the V6 engines also have a similar "G-cam" design, which wasn't successful in the 827?