It's not obviously contradictory. Openness to procreation has nothing to do with where the couple is vis-a-vis the fertility cycle when they have intercourse. NFP isn't foolproof, so even when one has the greatest chance of NOT becoming pregnant, an attitude of openness is still necessary, otherwise, conception becomes an "accident", which is never the case since God is the First Principle Cause of life. Can one increase/decrease the odds of conception by NFP? Sure. If I take a detour on my way home to avoid running into an annoying neighbor who I must be kind to, I still have to be open to being kind to that person if I happen to run into them anyway on my alternate route. I can't intend to kick him in the shin because I took a different way home. NFP is acceptable because it is part of the order of the reproductive cycle willed by God. Manipulating that cycle with synthetic drugs/contraceptives is
Manipulating that cycle with synthetic drugs/contraceptives is not.
Twist yourself anyway you want, but what you just posted is contradictory to this:
"each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life".
"Natural Planning" not being birth control makes as much sense as John Kerry, after many years of marriage and two children, getting an annulment, also approved by the Catholic Church.