Wring again.
The Commission as a body assumed that conception begins at fertilization. It wasn't just a "few" priests. It was the will of the body as a whole. The Commission took a vote on it.
I quote Bernas
AGAIN:
The unborn's entitlement to protection begins "from conception," that is, from the moment of conception. The intention is to protect life from its beginning, and the assumption is that human life begins at conception and that conception takes place at fertilization. There is however no attempt to pinpoint the exact moment when conception takes place. But while the provision does not assert with certainty when human life precisely begins, it reflects the view that, in dealing with the protection of life, it is necessary to take the safer approach.