No need to invoke metaphysics here. Whether time is an illusion or not doesn't depend on its "existence," though I'm not sure what you mean by "exists." I'm not convinced anyone does.
I agree with your overall point though. All we really need to say, when we say something is an "illusion," is that the phenomenon in question is not as it intuitively appears. Our expectations were one thing, but because of x, y, and z, this can't be the case. We think of it one way, but it's actually another way.
It's tempting to draw this distinction upon metaphysical lines, e.g., we thought it was one way, but here's how it Really (TM) is. Again, this is totally unnecessary and adds nothing to our scientific understanding.
I agree with your overall point though. All we really need to say, when we say something is an "illusion," is that the phenomenon in question is not as it intuitively appears. Our expectations were one thing, but because of x, y, and z, this can't be the case. We think of it one way, but it's actually another way.
It's tempting to draw this distinction upon metaphysical lines, e.g., we thought it was one way, but here's how it Really (TM) is. Again, this is totally unnecessary and adds nothing to our scientific understanding.