If you want an official source such as the Cathechism of Catholic Church, we don’t have because the official book does not go into these deep details of micromanagement.
But if you read traditional theology, casuistic books and read the historical archives of correspondance with the Sacred Penitanciary you would see these question treated.
For eg, vaginal douching that where popular in the past had always been condamned by the Church.
It is also common sense. We should not do something to try to avoid or decrease the likelihood of pregnancy whether it is prooven to be effective or not.
It is also a question of respect for the act, why would we want to evacuate the semen after the act is complete and we
feel (only feel) the semen’s persence is no longer necessary to procreation and we f
eel that it should not be there now for personal convenience only?
I am also absolutely sure that Billings and STM methods (formation and books I read) taught that the day after you have had intercourse you have to abstain because of the interference of seminal residuals.
I have a hard time to believe that Creaighton teach to evacuate the semen.
t only takes anywhere from 5 minutes to a couple hours for sperm to get to the egg and fertilize it.
depend on where we are in our fertile period. Spermatozoa can be stocked in the cervix for many days.