When citing a paper on arXiv, how important is the category? The arXiv documentation says that we should reference arXiv documents using references of the form:

arXiv:YYMM.NNNNv# [category]

e.g.:

arXiv:0706.1234v1 [math.FA]

However, most papers that I am aware of do not bother to include the category.  i.e. they have references of the form:

arXiv:YYMM.NNNNv#

Furthermore, I can't find a bibtex bibliography style which automatically includes the arXiv category (taken from the primaryClass in biblatex).

Also, the arXiv documentation page "Preparing TeX/LaTeX Papers for Submission" suggests that arXiv documents should be referenced using just the arXiv ID, e.g. arXiv:0705.1234  (i.e. without the category)

My question is: is it OK to produce a list of references without any arXiv categories (i.e. just arXiv:0705.1234)?
The arXiv documentation page on "Understanding the arXiv identifier" contains the following sentence which directly answers my question: 

"Note that the identifier no longer contains any classification information and thus reclassification after an article is announced is possible."