You know, all of this discussion seems to lack one specific concept. Maybe I have missed something I the three pages of posts, but I don't think so
Pros and Cons need to be considered from the perspective (pun intended) of the intended use.
While not really stated anywhere, I'll bet that most reviewers today write reviews based upon use with a Pentax K-series DSLR,
As a result, considering the impact on many functions, like P-TTL flash, which cannot work at all without A-Series or later lenses, lack of aperture data is a real con. On my PZ-1 it didn't matter because the PZ-1 had aperture coupling so the camera could do open aperture metering, and since the camera used TTL not P-TTL flash was not impacted and the loss of shutter priority was not really a big loss. But in today's world, where open aperture metering and P-TTL flash absolutely requires the A-series lens contacts, lack of the contacts is a serious con.
I am sorry that not every one has the same opinion, but you cannot change the fact that given 2 lenses, optically identical, one I K mount and one in KA mount, the lack of the contacts on the K-mount lens is a serious con.
In fact, being a k series bayonet might even be w con compared to an M42 lens, because at least with an M42 lens you can work in AV mode.
Let's expand this point a little more, to 4 optically identical lenses, KA, K, M42 with an A/M switch and an Auto M42 lens.
If you ranked them for functionality, the KA lens isobviously the top,
the KMount and M42 with auto manual switch would be debated for ease of use,
-auto aperture for open aperture focusing on the K but only manual mode for camera operation, with stopped down metering vs
-manual aperture so the need to manually stop down after cfocusing but Av mode for automatic exposure and metering.
The auto aperture M42 would be dead last, because it requires a lens modification to get manual aperture control or a very specific M42-PK adaptor.
Unless there is a global section in the lens reviews listing the pros and cons of each generation of mount,nwhich there isn't and which would likely get missed by most readers any way, listing what may seem to some as obvious to some, does no harm at all
Similarly, one might list an F or FA lens as having a con, because they are autofocus, if the intended use is video, where many prefer MF lenses.
Reviewers write reviews based upon what they use the lens for and equipment they use the lens with.
Live with it.
We have the same argument when it comes to overall rankings. From the perspective of optical performance, most lenses are , for all purposes between 7 and 10, but for lenses above 9 the price rises exponentially. Many people (self included) write reviews , as a result, based upon value for money. Clearly, 2 lenses optically equal, one costing 10-100x the price of the other should not be rated the same, one is very good value for the price, the other is not.
So let's not focus so narrowly on what some of us which the reviews to show, let people express what they think. As someone point out on page 1, otherwise we are hearding cats