There is a difference in quality of parable. One which is subtle and allows degrees of freedom in ultimate conclusion. There is another kind which constructs a (seemingly to the teller) logical path which the reader must "walk" for lack of a better term.
I'm surprised you haven't noticed such a dichotomy in life.
I would like to make clear, I don't necessarily understand either view point, but there is a qualitative difference.
of course I have noticed such dichotomies in life, parables are parables and some speak volumes more than others. However, they are just different fingers pointing at the moon, who is to say which finger is more important than the other?
Are there degrees of enlightenment? Are there rankings in how effective a koan or a parable is? I would have thought it is all down to what the receiver does with them. A 'high quality' koan might be wasted on a dullard, but a low quality parable might be just the thing that triggers off a productive state in a lively searching mind.
My rather flippant comment, was really to point at the "mine is clearly superior to yours" tone of response to Graham's story