We have to understand what we can reasonably expect from Ricoh Imaging - and what we can't. This isn't any sort of excuse (I've been accused to "excuse" Pentax when I say they won't keep up with Sony :rolling eyes
; but information on which we can decide.
It seems that Pentax was (is?) struggling with their production system. Long neglected - I doubt Hoya invested much - to the point high end lenses just couldn't be made. So they worked to solve that (and voila, their first high end lenses in a while).
I have no solid evidence, but it looks to me there is an effect i.e. fewer defects, in cameras and lenses. No, that doesn't mean zero defects; that is un-achievable at any cost.
Now they have to somewhat ramp up their speed, too.
Sigma has their Art series - the "speed" of introducing these lenses for the L mount, they're just adapting existing models. If you're comparing building in adapters on existing lenses with working on completely new designs, you're in for disappointment.