For most users, finding a value in a table is sufficient. They will then use it as they need, assuming that that number is the best available estimate of some specific nutrient in some specific food. While the first answer is probably true, the second is often false - in general it does matter. In general, apparent and unexplained inconsistencies reduce the confidence in all such data, in the system which provides such data, and in the science that works with such data. The problem hinges on the fact that it is unlikely that these data really are inconsistent - they only look inconsistent.
Most data bases present a single value for a specific nutrient in a specific food.
This leads back to the first answer above - that different things were measured. While it is important to realize that there are a number of specific sources of food composition data variability, the major point is that few tables even hint that such variabilities exist. Moreover, those tables that do, such as those shown in table 2, do not do so in a consistent fashion, nor are they very helpful about just how to use this added information. Foods are not mathematical ideals, but must be considered as probabilistic or statistical objects, with statistical distributions of their nutrients. Any compilation or use of food composition data must be firmly based in this fact.