I'm not sure I'd say immediately flat, but fairly promptly.
That wasn't my concern though. The issue is that the foot must not stop or even pause at flat, it needs to go right on through to the toe, with the heel lifted by the end of the step which is when the left foot draws even with it. If you keep the heel down as you move into step two, you don't use the foot to generate a pickup and send the hips into the swing. Without the hip leading, the swing will be be broken and lead by one or both of the left foot or upper body instead. The common way to make a broken swing like this feel full is to save a lot of the rotation for the early part of step 2 - a mistake, since the action is CBM on 1, not body rotation on 2. Get the heel up to generate an aligned, hip-lead full body swing, and on time rotation doesn't rob anything from the step the way it does when the full footwork of step one is neglected.