Man, that really misses the point of minimalism. The empty space is what makes you focus on the one or two elements that are there. A cluttered poster just makes your brain tired trying to see everything at once.
But minimalism is really about taking things away until only what's needed is left. It's not just empty space, it's about removing everything that isn't essential. That act of subtraction is what forces you to focus.
Oh wow, we're really splitting hairs over what subtraction means now. So the magic isn't in the empty space itself, but in the super special act of making the empty space? That's like saying the best part of a cake is the act of baking it, not the eating. You're both just describing the same thing with different words.