Chess study which is correct

There is a famous chess study by Theodorus Kok with the famous key move 1.Na8!!! The chess study is completely correct if you shorten the solution and don't play it out to mate. The same applies to the chess study by Peter Krug. Here, too, only 1.Na8 wins!!! But the study should end after 6.Na4!!! Because from then on Black can no longer hold the opposition with the black bishop and there are several roads that lead to Rome. Peter Krug didn't realise this at the time. As a result, the chess study in the Harold van der Heijden database, which was in itself completely correct, was given as cooked, precisely because the solution was inaccurately continued to mate. The video is old and there were no good smartphones back then. The video quality is therefore not good in terms of sharpness. The video about chess composition was recorded in the city of Salzburg.