The minimum time in ranked to be accelerated promoted to corporal in the PRes is one year, so likely there is something else at play that is getting your friend promoted if it is earlier than that.
Reference is CFAO 49-5(20). The mitigating factor is the CO is not the approving authority but the commander of a command.
19. Accelerated promotion may be approved only by the commander of a command.
20. A CO may nominate for accelerated promotion members with outstanding ability, or leadership or supervisory potential. Accelerated promotion to Cpl must be in recognition of demonstrated outstanding performance as a tradesperson, whereas nomination for accelerated promotion to MCpl or above must also recognize leadership potential. A Pte may be nominated for accelerated promotion to Cpl or MCpl but a member of the rank of Cpl or above may be nominated for accelerated promotion only to the next higher rank. A member must have a minimum of one year's time in the current rank or appointment and have obtained the prerequisites for promotion in accordance with Appendix 1 or 2 of Annex A, as applicable, with the exception of the normal time requirement.