Oh, it's incredibly common. Aside from companies paranoid (perhaps justifiably so) about sensitive information leaking out through the interview process, by default many companies use at least the initial stages of the process as a kind of a "one-way mirror" -- in which they're scrutinizing you for ticks, fleas, what-have-you, and only in subsequent stages do they lift the skirts, as it were, on the actual projects you might be working on.

With the apparent basic message in mind that they (and their projects) are so self-evidently awesome that they shouldn't have to bother trying to sell you in the idea of working for them (by say, letting you know what you might actually be working on).

But it could also be much more mundane than that. Sometimes the reason they won't go into details is because they've already decided to pass on you, and so they prefer to cut the discussion short to whatever extent possible.