Are you serious? Do you even know for how much time the problem exists? Have you been reading the forums? How many persons here said they can replicate the issue EVERY TIME and EVERY TIME the issue is with the same processes that fail to quit during shut down?
This is exactly the same as the issue with reduced performance on 15" rMBPs. It was there since forever but Apple only cared to fix it once people started seriously complaining. Once that happened, Apple took 15 days to solve the issue by updating the EFI. Maybe they were testing it for months. Or maybe the timing was a mere coincidence