problem with that coverage range is it is still coming from a source the size of a quarter. Anything not directly looking at the light will be nearly completely shaded. Even if it will throw the light 3 feet, I would never personally use, or recommend using any less than 1 dense matrix style led fixture every 12-18” of length If the user will be keeping any appreciable amount of branching coral.
Put ONE dense matrix smack dab in the center of a 24” cube, and the entire sandbed may be illuminated evenly, but any branching coral not situated directly under the point source will be half shaded. Yes, there will be a minuscule amount of back scatter from glass and sand, but not enough to make a big difference. There’s an easily dismissable but extremely important distinction between raw spread, and realistic coverage.
If keeping mostly encrusting corals or corals which are soft and wave around In the current, it is less of an issue since by design they will not self shade