findMap() does not use/hit natural key cache

[rbygrave]

Steps to reproduce

Entity bean with @Cache with naturalKey

@Cache(nearCache = true, naturalKey = {"app", "key"})
@Entity
@Table(name = "app_metric")
public class DMetric extends BaseDomain {

Query with `findMap()' that ought to use the natural key cache

    return new QDMetric()
      .app.eq(header.getApp())
      .key.in(keys)
      .key.asMapKey()
      .setUseCache(true)
      .findMap();

If the above query was findList() it hits the natural key cache but findMap() does not.