Cam lobe wear is ONLY a critical issue on pump-deuse injector motors. Anything with a common-rail hpfp and piezoelectric injectors does NOT have the extra cam which takes up space and makes all the cams the limiting factor.The big deal about 505 and 507 is specific protection for cam lobe wear. 507 is for dpf and 505 is non dpf. The way the tdi engine is designed, it requires a specific oil to prevent premature cam lobe wear.
Any modern diesel oil can deal with dpfs, but only 507 can deal with cam lobe wear prevention.
To the op - all the diesel manufacturers qualify the engines/emissions control systems as a unit. The proper additive package in the oil is just as important to correct emissions control function as the O2 sensors are. The additives (think zinc which USED to be a common anti wear additive) CANNOT be allowed to contaminate catalytic surfaces. If that happens the emissions systems fail. Hence, many manufacturers are pretty insistent that ONLY listed lube oils be used. Also, manufacturers are required by US law to make sure alternate sources of maintenance consumables are always available WITHOUT having to purchase from the dealer.