Yes, in sequential pattern mining the order in itemsets should not be important. However, for practical purposes, all itemsets should be sorted according to some order in your input file, as explained in the documentation:
Note that it is assumed that items are sorted according to a total order in each itemset and that no item appears twice in the same itemset.
That order can be any order such as increasing order or decreasing order but it must be the same for all itemsets in your file.
Now, having said that, I want to also tell you that this particular algorithm for valued items may not alway generate the same result. The reason is that this algorithm applies k-means internally. Since k-means is a randomized algorithm, each time your run it, it may generate different clusters. Thus for this reason, if you apply this algorithm several times, you may get different results, even with the same input file.