I agree with not always knowing what they want, some adverts are quite misleading. Another thing I have found is that a lot of adverts state must be able to drive(I don't) They will get someone to work out of two places, cheaper than employing two people.
I answered an ad once, all it had in it was a job title and a phone number. I was invited to go for an interview, great so far. They then asked me back for a second interview, only then did I find out they wanted me to start there and then. The job turned out to be nothing like I expected, unfortunately the majority of people who phoned up were Chinese. Nothing wrong with that, but I got fed up saying no I don't speak Mandarin, I felt like saying I don't speak it but I do eat it.
The boss decided I was not suitable for the job, a little more information and honesty and we could have both saved our time.