It really doesn't matter. The people who write these questions know that this is a source of confusion during this period and have written the questions in such a way where it really does not matter. You will not be asked about subtypes of schizophrenia. You won't be given a high functioning autistic guy without language impairment and be asked to determine whether the diagnosis is ASD or aspergers. You won't be expected to decide whether someone can be classified as schizophrenic with a single Schneiderian First Rank Symptom.
It's a good question about when this stuff becomes fair game but I can say that as of a month or two ago, when I took the shelf, the questions were designed this way. I did very well on that exam and my version of FA Psych still used DSM-IV.
If you have two resources, though, all else equal go with the most recent one.