"Simultaneous" is a word that you use from within time, to refer to relations described by time. I don't think you'd use the word that way if you were really looking at the universe at the level of timeless physics, really seeing the whole design in every facet. (Though it is the word you'd probably use if you were a human author trying to write a character who sees the deeper reality beyond time, if you yourself don't quite see it. :P) Probably the intuition behind that is imagining looking at spacetime as something like a film reel laid out in front of you, and seeing that it's all already there, no matter what the people in any given frame seem to think. But that puts your perspective outside this universe's apparent time dimension, but inside an imagined outer timeline against which you can continue using words like "simultaneous" or "already". And that's no way to really reduce time; it's a mistake similar to trying to reduce consciousness by putting a little homunculus inside your head that watches your sensory input on a projector screen. It's reducing a black box to some visible machinery interacting with... another copy of the same black box.

I don't think there's any perspective from which "Time is simultaneous" makes sense, unless our universe is actually a static block of already-computed data on the hard drive of some computer in a different reality with its own timelike dimension.

(Edit: Oh, and Dr. Manhattan is being a bit uncharitable by claiming that "humans insist" on seeing things in this limited way. Sure, I consider my lack of omniscience to be a moral failing on my part, but that doesn't mean I'm not trying to do better.)

Hey, no quoting yourself.