Fr. Euteneuer teaches what the Magesterium and the Catachism states. He does not make the rules as he goes along.
The best kept secret in the Church today is Natural Family Planning. This is perhaps because progressive Catholics, who control most of the Church's teaching apparatus, have never focused on it. They think it part of the baggage of Humanae Vitae, a document they condemn out of hand without really pondering its contents.
Its result is heinous though. God gives positive commands to multiply, and calls children a blessing. Euteneuer stubs all this out and then slides in under a technicality of avoiding explicit edicts of Humanae Vitae of articial birth control.
His process and program is most destructive however. It basiically destroys catholic progeny, allows for family planning at a percentage far greater than anyone ever claims for condoms. Irony of ironies......
No one knew of such science-based process prescriptive methods until the last 15-20 years. Explain the same program to St Pius V or X and what would they say about it? They would throw up and the former would flog him.