What makes Lissa an ironclad fleet battle?

Why describe Lissa as the only ironclad fleet battle when ironclads also fought in South America and Japan?

The distinction is a substantial squadron of ironclads on each side, not an isolated encounter involving one or two such ships.

A fleet battle between ironclads involves substantial squadrons of these ships on both sides. Smaller actions in South America or Japan could involve only one or two ironclads among the opposing forces. The distinction concerns how extensively the new technology equipped the fleets. It does not deny that ironclads fought in other engagements.