No, dark energy kicked in much later. And I don't think it's fair to call it a fudge factor. Rather, the evidence shows that the universe's expansion is accelerating; "dark energy" is just our placeholder name for the as-yet-unexplained phenomenon causing that acceleration. A fudge factor is when you massage the data to fit a desired model, like Einstein's cosmological constant, which he proposed in order to cling to his belief in a steady-state universe despite the evidence showing that gravity would cause its collapse. This is the opposite of that -- it's an attempt to explain the evidence, not cancel it out. Just because it's admittedly vague doesn't mean it's dishonest.