Spray Foam Insulation and Vapour Barriers

We just had an insulation inspection done on a usable space attic (spare room). Insulation is closed cell spray foam, R31 in rafters along roofline and R22 on the short exterior pony wall. We were asked to put vapour barrier (full coverage plastic sheets) with Tuck Tape. Rafters are 2x6, so the spray foam is not continuous but completely fills all space with the exception of about 1 inch of rafters. However during the inspection, where the pony wall has more than 1 inch of space between barrier and insulation, we were asked to make slits in the vapour barrier to allow trapped vapour to excape. The pony wall is 2x4 construction on a double brick exterior (circa 1910) so 3.5 inches from the exterior wall.

So the question is. Why put slits in the vapour barrier to relieve trapped moisture? The entire cavity between rafters now has a 12 inch slice at the bottom, which now defeats the purpose of the Vapour Barrier?

Huh?