I think it's just the nature of their client base. Universal is farther away from destination maturity than Disney and has to be more careful in the way they market themselves. They're in a period of rapid expansion which is tricky for a destination to do properly--my guess is that they don't want each of their upcoming projects to cannibalize one another so timing is everything. If they announce Kong too early, people will postpone their 2015 trips to 2016 and since they don't have the same built-in base as Disney does that would hurt them. They also are more reliant on a local market than Disney is, and keeping locals excited at just the right times (not too soon, not too late) is crucial. Meanwhile Disney knows they'll get x amount of visitors coming in from all over the world no matter what, and that since they depend more on people who make bookings/reservations far in advance, have to publicize everything as early as possible.
I think they're both frustrating because with Disney you get excited for projects way too far in advance and with Universal you're left anticipating "unknown" projects for a longer amount of time. But I think it's their way of keeping things exciting and seeming like they're moving at a steady pace. Their steady pattern of announcements at later times gives the impression that they're adding more, and more quickly, which appeals to the demographics/psychographics they want to capture.