I think it's a fashion trend. Fat is in. Manufacturers need to sell skis. We had the new short radius skis; now we have the fat skis.
No I have not skied the new supposedly great at carving ice fat skis. However, after riding a Honda CB750, Yamaha R6 and Honda Interceptor, I don't need to ride the GoldWing to tell you that it won't be the best bike to take to a race track. In my experience, things are already becoming a little less satisfactory in the high performance department on hardpack and ice when I go from an SS speed to an SS magnum. Yeah, yeah, I know; it's the Indian, not the arrow, but you can't ignore the physics of a ski that is under torsional load needing some flex and having a different effective edge angle at the tip than under the boot. It makes a difference if you are carving a high-g edge-locked turn on a really hard surface, and some people like to do that, even if they are not racing anyone.
Two mitigating factors that allow the 105 to be an "all mountain ski"
1) It does depend a great deal on which mountain. If you are skiing in a typical sloped skating rink with rocks in Ontario, then a 68 mm ski will be fine. Less force is required to tip it to a big angle as you lever it against the ice, and so long as it's not too short for you and you have some skills, you can handle a foot or two of snow with no problems. If you are on a mountain with deep snow, even on groomers just weighting one side of your foot is enough to tip the skis to any angle you want, so you don't really notice the width when carving.
2) It depends a great deal on how high a performance level you will be satisfied with from your "all-mountain skis". Most people cannot pull 2 or 3 g turns and cannot really carve a pure edge-locked turn anyway. They are happy making easy-peasy turns with lots of speed control smears down the blues. The performance is called good, but it's really "good for an all-mountain ski", not good compared to a race ski. People aren't expected to exert high performance demands from their all mountain skis.