Glide path

That is not how this works.

The question after the caution is, where is that vortex right now? And does my flight path intersect it? If you're flying a visual approach behind a heavy on a three or four mile final, you need to be tracking the lead aircraft's glide path relative to yours.

The vortex sinks.

If you're above the heavy's glide path, you're above the primary vortex concentration.

If you're on the same glide path, you're likely in the vortex zone.

If you're below the heavy's glide path, you're flying into the area where the vortex has already descended.

That last scenario is where the wing drop comes from.

The accidents that shaped our understanding of wake turbulence hazard are worth knowing in some detail.