A couple of things.....
First, ski manufacturers use base material that comes on large rolls. While it is possible that a small section of a roll of base material was somehow out of spec, that is not likely. Therefore, were the base material to have been out of spec, it would be reasonable to assume that they got a whole roll of out-of-spec material and, thus, the problem would be more widespread. Note, unless they are publishing an extraordinarily in-depth array of specifications, there is no way to know what "spec" is for this model, during this particular production run, at the time it was made. And were they to have spec'd a thinner base material for this run, there is no guarantee that such a decision would create an arguable fitness for purpose issue, as the product is for skiing on snow, not rocks (undesirable is not necessarily unfit, from an implied warranty perspective).
Second, just because it is unlikely (though not impossible) that a single pair of skis would have out-of-spec base material, that does not mean the base could not be out of spec. Skis do not come out of the press finished, nor do they always come out flat. It is entirely possible that this pair, or even one of the skis, could have needed (or gotten, even if not needed) extensive grinding at the factory, before the OP ever got them.
Overall, though, I would say that we do not have nearly enough information to make any sort of intelligent assessment. Yes, the skis are in rough shape. Yes, there are obvious maintenance issues. None of those really has anything to do with the OP's question, which is essentially along the lines of "should my bases be this thin without having been ground?" Again, not enough information. The best repair would be to cut out that section and base-weld in a new piece (well, actually, at this point it needs more than base work, so assuming the restorative work were done...). Were the OP to do this, he could then measure the base material thickness and provide some meaningful information. A 2-D picture from the top is not illustrative.
In short, it is entirely possible that the base on this ski is abnormally thin. But not likely. We cannot offer any meaningful assessment of this from the information given.
The fact that the carbon stringers are visible through the bases has no bearing on this question, nor does it offer any meaningful insight. The translucence is simply a function of the pigmentation in the plastic.
Just because the fine folks in warranty departments hear things like "I was just skiing along" and "I never even hit anything" so often that they even have pet acronyms for these lame excuses for obvious damage, doesn't mean that every now and then it isn't actually true. However, absent some obvious empirical evidence, the prevalence of skier fault returns means they are not likely to believe it. Obvious neglect and poor maintenance are only going to strengthen the likelihood of that negative response.