Leader behaviour is described on two separate axes, not one authoritarian-to-democratic continuum; the Ohio State studies found every combination in practice. Task behaviour is how far the leader spells out duties and responsibilities, one-way: what to do, how, when, where and, where several people are involved, who. Relationship behaviour is the degree to which the leader communicates in both directions, or among several people: listening, facilitating and supportive behaviour. The two are separate dimensions whose four quadrants give four basic styles. Being directive is not being unpleasant, and the dimensions are observed behaviour as the follower perceives it, not attitudes (the Managerial Grid's concerns are attitudinal). In families or with human-relations trainers the words guidance and supportive behaviour may replace task and relationship, but the definitions do not change; explaining why straddles both dimensions.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.