Why do markets ID 70 and 130 (Correct round score - map {map}) share the same name but each expose only one variant?

The two markets are distinguished by their market ID and variant, not by their name. This is a historical artefact of how the markets were originally created. Market 130 (variant mr:12) is the one actively used, while market 70 (variant best_of_rounds:16) is kept only as a backup in case it is ever needed again. For current integrations you can effectively rely on market 130.