Nice little rundown, Charley. As you know, I'm more of a mild & street guy instead of an MT guy, but I've scrutinized mountain bike tire options for years. I know that's a very different animal (narrow, very different functions in the front/rear, much smaller forces to deal with, rotation is a non-issue, directional or non directional patterns equally easy to use), but what I know from that does make me feel like more, smaller tread blocks reduces mud effectiveness (assuming smaller gaps between the blocks as well). I don't know squat about the Hankook, but whenever I've seen it, that has been my thought (also that they must be loud on the road). Maybe auto tires don't follow the same rules; heck, even some bike tires like to defy logic for better or for worse. Kumho's MT, and the red-letter General Grabber come to mind as tires that really stand-out as well.
As you and Dave have done to an extent, maybe the key to understanding some of this is to understand the reasons for the little differences within these tires or to look at why the other tires (MTR K, Kumho, Hankook, etc) do it their way instead.
I'm glad you brought-up road noise. That makes a lot of sense in a lot of places on these tires, and I hadn't really given it much thought because my personal thinking when designing an MT tire wouldn't give road noise much attention since I feel that anyone buying an MT tire wouldn't be spending a bunch of time on the street and would be more concerned with their off-road performance. There are a lot of people who DD on their MTs, and there are a lot of "posers" out there, so I can see how road noise is still a priority here.
As a general rule, larger tread blocks means larger voids, which is better in/on mud.
With larger tread blocks, there's only room for 4 blocks wide. IMO
However, larger tread blocks means less edges, which means less traction on wet pavement, packed snow, and ice. Hence MT are traditionally not ideal on those surfaces. To try to improve this, some add sipes, some add silica to tread rubber, some make the treadblocks smaller and more of them.
If you do enough of those improvements, at some point it's no longer an MT, and has become a hybrid tire (or aggressive AT if you prefer that term).
Once the design has changed enough to be a hybrid (instead of MT), it has lost some mud ability, but gained traction in those other areas, and become more street friendly to.
If you did even more changes to a hybrid to make it even more street friendly, it'd be an AT.
My point is that we think of tire types and categories as being black and white. In reality, there are many shades of grey where categories overlap. Then add in use of terms, which differs between companies and people, and things get murky.
Road noise matters for MT. Not just for mall crawler pavement posers. Guys who go in mud still like to have less noise on road so they can have a conversation with a passenger, hear tbeir cell phone, hear the radio, or just not have a head ache on the freeway.
Alternating tread block sizes (inner and outer lugs) reduces road noise without losing any traction.
Alternating outer tread block length reduces road noise and increases traction by increasing digging and self cleaning.
Sipes have obvious benefits for traction, and they make tread quieter too. I'm surprised most MTs don't have more sipes, but if they did they might be called hybrid tires.
This has nothing to do with road noise, but is important to mud traction.
The little ridges between treads (on some tires) are called stone ejectors (or other names) and are there to protect tire from stones and reduce stone retention between treads. However, they have the addtional benefits of increasing self cleaning of mud and snow by helping break the suction that prevents self cleaning.