I'm saying that most skis are effectively all-mountain skis in the hands of a skilled skier, regardless of their labels, and regardless of how we might classify the skis. An obvious exception (IMO) would be a rockered powder ski, which has a fairly narrow mission and is not something I would care to be carving on.
Out of my quiver of 4-5 skis, only one pair (my mid-fats) is officially designated in the all-mountain category by marketing speak, but I ski all of the skis as all-mountain boards. I can't see a reason why they wouldn't be considered all-mountain skis by most standards. Yes, I have to accept certain weaknesses to take the skis out of their target element, but it's not a serious compromise.
But that leads to an interesting question, sort of related to my IMO above. What skis are *not* capable of being all-mountain skis in the hands of a good skier? In other words, what ski has such a narrow focus that it's weaknesses outside that focus seriously detract from the ability to be an all-mountain ski?
I have a 3 ski quiver
-im103 which is a super stiff damp, straight ski I use for charging hard in a variety of conditions. Super stable at speed. Want to be driven hard in turns. Super in crud and setup snow. Good grip on piste. Straight and stiff, not horrible in bumps.
-Scott P4 Not a real charger ski but more of a fun and easy buttery soft snow ski. For pow days and a day or two after. Trees.
-K2 PE which I haven't mounted up yet. Basically a skinny ski for days when it hasn't snowed in a while but I don't want the challenge of the m103. Should be good on days when I am looking for bumps.
I can rip groomers on any of these assuming its not bullet proof. If its BP then the scotts lose out on the grip, but I can still work them. Bumps are doable but alot of work on the m103. Pretty good on the P4. and probably much more fun on the PE. In crud the m103 is clearly the destroyer. The P4 floats over heavier thicker cut up and crud easily. The PE I am curious to see how it does. On deep days the P4 is a super floater. I am heavy enough to flex the m103 but its still a bottom feeder in pow. The PE I have heard good things in pow and I want to see how it works. The shape of the PE is similar to my nordica beast (long lowrise tip) which I converted to my AT skis. But the PE is slightly narrower and slightly stiffer. I guess you could say they are all all mountain skis.
I think skis on the extremes of flex, running length (rockered skis have a VERY short effective edge), turn radius, width, will be much less versatile than ones that fall more in the middle.