Caves, in general, don't move much. NPC's, on the other hand, do. What the OP didn't mention was the part about animations, which is actually where the performance gain comes in. Two pieces of armor means two meshes that have to be deformed. One piece, one mesh. It's a valid issue, especially if you want to have lots of NPC's on the screen. Given enough NPC's, the savings of combining the armor really adds up.
I don't like it either, but there is a performance advantage to making the armor one piece - especially on resource limited platforms.
Armors are made up of many different pieces (and I'm not just talking about boots/gloves/helmet). Just look at the 'bare chest' armor on one of the screenshots. It has to be made of at least two different pieces (armor part/skin part). Now look at all the so called armor variations with different pauldrons etc. All those little things are
very likely independent pieces. If you still have no 1st person whole body rendering in Skyrim (and looking at the trailer it likely will be that way) then the armor even has to be made of several different pieces anyway. Whether an NPC is made of 20 pieces or 21 pieces doesn't matter. Especially when a
huge amount of other things (whether they're rigged/animated or not) is stressing the CPU/GPU. And certainly claiming that they can 'put more people on screen' due to that change is a ridiculous exaggeration.
One object like a simple rock may be less detailed, but the total amount of triangles rendered per frame or larger objects like houses are not. Actually an armor mesh will be tiny compared to the total amount and equal to a house for example.
No idea about backface culling, but that doesn't make a difference for the amount of objects. Occlusion culling they had in FO3, but only for interiors.
Rocks and the like have been separate models in Oblivion, FO3 and I'd be very surprised if they were not in Skyrim. And there are tons of different objects in a single scene where your vertex manipulation method wouldn't work anyway even if they used it.
To me it's as obvious as something can be that merging a single object in the whole scene (even if there are 20 NPCs on screen and thus 20 merged objects) is not going to improve performance noticeably. You also have to keep in mind all the other things that matter when they say 'we can put more people on screen'. More AI (!), more animations, more dialogue/sounds etc.
The only way to prove this 100% is to get the game, split the greaves from the cuirass and look at the difference. Just like some people wouldn't believe that my car doesn't drive faster when I remove the cigarette lighter from it until they actually drive with my car with the cigarette lighter removed. :shrug:
There's no point in arguing with Phitt because he knows everything there is to know about programming and exactly how the Creation Engine and it's new renderer works. :rolleyes:
There is no point arguing with a really devoted fan because he will believe what Bethesda tells him no matter whether it makes any sense at all or not. It's funny, because you don't need to know much about rendering engines to understand that this is nonsense. You just need to look at the bare numbers. Unless the Creation Engine has a special problem with meshes called 'greaves' this is pretty obvious. But in that case renaming them would probably be the easier solution.