First off, how do we know that it's actually true ? Where are the surveys by objective standards executed by non-Nazis that show this 'fact'? In a totalitarian state every bit of information is suspect because it's most likely propaganda.

Secondly, if true, how would on go about to prove that this is an achievement of Nazism and not of German culture in general (cf. the irrelevancy of the contemporariness of Porsche's designing of the VW). After all, the proverbiality of Grundlichkeit of the Germans indicates that punctuality has been highly valued there regardless of the enveloping ideology. If the trains rode on time in the 60's, 70's and so on until today too, then the achievement is German and not Nazi.

Thirdly: so fucking what if it is.
The goal of the extermination of the Jews and the 'purification' of society by physically eliminating all opposition and all that did not conform to the insane racist standards of Nazism were on the books from day one. It's one hell of price to pay to get the trains running on time, since that's an achievement that pretty much any ideology manages more or less.