Pre-PD TDI had cats and EGR using ACEA B3 and B4 based oils (VW 505.00) and 502.00 high-SAPS oils were used back then, and still today, for petrol engines.
I think emission system is much more complicated on PD then on pre PD-TDI. I had those engines in Europe, both with 90hp and 110 hp (variable turbo), and had Skoda Octavia with 1.9 105hp, while my brother has now 5 PD cars and several CR cars in his car pool for business he owns.
Those engines are Euro III, PD engines are Euro IV and some Euro V, and with that have more complicated emission system.
I am not sure that VW 505.01 is anything more stout and more capable of protection then VW502.00. Primarily, 505.01 is emission protection oil.
Actually, in Europe, VW 504.00/507.00 proved much more suitable for PD engines. My brother uses Repsol 5W30 that meets VW 504.00/507.00 in all cars, and no car ever had any issue, and some are clocking more then 350 k km.