Sealing EPDM Rubber Membrane seams using QuickBond Seam Tape

Plytech UK's Marc King shows how to create a seal in EPDM Rubber Roofing Membrane. In this video Mark uses QuickBond's Seal Tape and Primer , RubberCover EPDM Rubber Membrane.

[@larryseibold4287]

It seems that the primer is a thin adhesive. why is the tape (additional layer of rubber and two extra layers of adhesive) needed? Everyone does it this way, but i dont understand why. the cost difference is very large, so there must be a reason why adhesive alone does not work for EPDM membranes.

[@allenpritchard2715]

Is there anyway of installing in one piece when the osb box is already fixed in place?