Smoke "spotting"

[Blackcloud6]

The optional rule for smoke says "Unless forbidden by scenario special rules, all mortars, on-board artillery units and off-board artillery increments conducting bombardment attacks have a limited ability to fire smoke or illumination rounds instead of causing damage."  Note it says "fire" and not "bombard" or "bombardment."    In the procedure it says: " For each unit or artillery increment firing, the active player designates a spotted target hex within range and rolls two dice."  Note the term "spotted hex."    And no where does this say it is technically "indirect fire."   So "spotted hex" seems generic enough to me to mean any hex spotted by a any friendly unit although one could assume a leader is needed as only a leader can direct indirect bombardment fires.  But the smoke rules do not specify so am I correct to safely assume that the spotted hex be designated as long as any friendly unit can spot it?