My previous post should really have been titled "Not defining one's work", and it occupies one extreme position that I have run into at various times.
Of course, I have also run into what Bradley Peters in an email to me called "the polar opposite": A photographer overdefining her or his work. In his email, Bradley notes that this doesn't get talked about as much; but it certainly seems to be very common, too.
To quote Bradley: "Instead of not being able to define what one's work is about, the [photographer] ends up having a very well defined idea, but the work just ends up being an illustration of that idea and leaves very little room for anything else." Just yesterday, I did some portfolio reviews, and I ran into this more than once.
There are many different aspects here, too, and I'll probably miss many of them in the following; but it might be worthwhile to talk about some.
First of all, as an artist you will never be able to perfectly define (or predict or predetermine) how people will react to what you produce. Somebody will always find something that you have never thought about, and that's basically what makes art art. Art is about freedom, and as an artist you want to give your audience that freedom, that possibility to explore and to experience. The more you take that freedom away, the more your art suffers, the worse it gets (btw, this is why so many public art projects are so unbelievably bad).
If someone sees something in your art that you have not seen that's a good sign - and no artist should aim at restricting this, no artist should refute anything here.
In an art school context, what I have run into is young artists having an idea and then fleshing it out in unbelievably elaborate detail - adding new details when photography is coming in that doesn't quite "fit" what they have. It's like putting yourself into a straightjacket, and when you notice you still got some wiggle space you ask someone to pull it even tighter. This is how you then (at best) end at the "illustration of that idea" Bradley talked about.
Somewhere else in his email he writes: "I don't think there's a problem with talking about one's deep urges or a personal idea [...] but I have also seen where this information sometimes becomes a crutch. It's a way for people to talk 'around' the work rather than 'about' it." (my emphasis)
Ultimately, there might often be the same fear that makes some people refuse to talk about their work: You're so worried to actually discuss your work (and to discover flaws or ways to improve it) that you build a big, solid shell around it, which nobody is supposed to pierce. You're hoping to prevent a debate.