I will answer this question instead of the PCR Moderator as it does not specifically refer to this PCR, but to the general LCA approach used in the International EPD System.
As you know, the general principles of attributional vs. consequential LCA methodology is well established in the scientific litterature. The mention of attributional approach here is not intended to give a full explanation of the system approach of the International EPD System.
This is instead done in the General Programme Instructions, Annex A, which I refer you to for additional information.
Secretariat of the International EPD System