You are correct that many Christian believe that pregnency begin before implantation
but all Christian do not believe this and many believe in the medical defination of pregnency. Also doctors believe that pregnency starts after implantation and embryonic stage starts after implantation.
some believe that life/soul comes after implantation and some believe that it comes before implantation. Doctors do not comment on this because this fact is not establishes even amongst religious Christian leaders. Defination of abortion
STARTS AFTER implantation there fore emergency conteraceptive pills are not believed to be abortifacients. Now you have to judge that wheather unfair misinformation is from doctors side or from religious people who have not still decided from when the life bigins
Hope this helps