I have the Novoflex. It does the (tedious) job of changing aperture perfectly, and unlike other brands, I know it's well made and sits absolutely flush with the mount. As Roger Cicala has pointed out in the past, the slightest tilt from a $7 adapter and what you've basically done is decentre every lens you put on it.
If you're not a pixel peeper, you might shrug your shoulders.
Camera companies work on that basis ... they save costs on rigorous quality control, sell lenses that might be decentred, and there will be many poor owners who don't realize they've bought one not up to spec.