Very few Rumba figures have steps falling on beat one. The major exception is the Spiral, with its delayed forward walk, pointing the foot, without weight, on four, and stepping with turn ending in a spiral cross on one.
Actually, lots of rumba figures ARE danced on one, at least here in the UK, because sequence dancers seem completely incapable of dancing on the correct beat; and if you are the only couple in the room dancing "on two", you have to concentrate like hell, and get very funny looks. Such is life.