Actually, most medical experts today would completely dispute your statement about how birth control pills work.
Both this writer and you posit a Middle Age Natural Law concept as the ultimate foundation and then basically argue for a heresy - biologism.  The Commission was about much more than just *how the pill works medically*.  You interpret any form of *interference* at any time as if it is abortion - it is not.  IUDs do not cause abortions unless you begin with a belief that life starts from conception (at the latest) and sperm/ova, at the earliest.
No medical science supports this reasoning - it is a belief based upon faith.
VII and John XXIII asked that Catholicism be updated with the latest in science - this link and your bias rejects this in favor of a black/white idea.  Faith is an action; relationship, and journey - not a cathecism statement.