Aggressive bullpen = manager is more aggressive with letting his pitcher work out of a jam, ie. he's slower with the hook and pitchers will stay in longer.

Conservative bullpen = manager will not take as many chances with letting a pitcher stay out there that's getting into trouble.

That's how I make sense of it after I discovered this last season and made the post about it. It's perceived as being "backwards" but when you think about it as I described above, it actually does make more sense.

Jon