Answer

You need to distinguish between the mathematical-theoretical field of statistics, which is a branch of mathematics just like any other branch of it, and its application in the world. Applying it in the world involves various assumptions, and those are of course not necessary truths. Just as applications of other branches of mathematics are not necessary truths, because any application always assumes things about the world. See column 50 about this, among others.
For example, statistics (really probability) says that the chance of a particular result on a die is 1/6. There is an assumption here that the die is fair, and that is not certain. Beyond that, it is clear that any particular roll will yield a random result that statistics cannot predict. If you make a great many rolls, then by the law of large numbers the distribution will approach the theoretical probabilities (1/6 for each face), but even that may fail to happen in practice, because that is the meaning of a statistical prediction. Still, the statement that the probability is 1/6 is mathematical and necessary. The problems arise only in the applications and uses.