^ They definitely do. Positive or negatively pressurized, you NEVER want open area next to a fan that creates a short loop or at best, still be countermining the pressurization's intended effect and reducing effective airflow.
It's only going to have positive pressurization if you screw up the cooling by having all those open areas next to the rear exhaust fans, otherwise your rear exhaust, from two fans (plus PSU also pulling against the front intake if it doesn't have its own exterior intake) should at least be as strong as the front intake, especially in recent years where you don't need turbulent flow from the front fans to help cool as many (if any) HDDs in a front rack.
Of course there are benefits to positive pressurization still, mostly to use filtered intake panels but then we get back to the same issue, that then you also want to block off all passive areas next to fans but this time the more critical area is the intake fans. Both intake and exhaust should not have these areas of leakage adjacent to them.
Fresh air to the GPU would come in the front of the case or a side panel. The perforated area in the back just robs it of more than if it weren't there because any air the adjacent fan moves, only flows straight to the fan and robs the case of the airflow the fan otherwise would have pulled from further away.
This isn't only true for computer cases, rather any typical application involving a fan. The purpose is to move air. If you don't need as much air moved then throttle back the fan to save dust, noise, and wear.