spring-boot-configuration-processor cannot generate metadata for nested class

When I have following class defined in project

@ConfigurationProperties(DUBBO_PREFIX)
public class DubboConfigurationProperties {
    @NestedConfigurationProperty
    private MetricsConfig metrics = new MetricsConfig();

    public MetricsConfig getMetrics() {
        return metrics;
    }

    public void setMetrics(MetricsConfig metrics) {
        this.metrics = metrics;
    }
}

public class MetricsConfig {
    private AggregationConfig aggregation;

    public AggregationConfig getAggregation() {
        return aggregation;
    }

    public void setAggregation(AggregationConfig aggregation) {
        this.aggregation = aggregation;
    }
}

public class AggregationConfig {
    private Boolean enabled;

    public Boolean getEnabled() {
        return enabled;
    }

    public void setEnabled(Boolean enabled) {
        this.enabled = enabled;
    }
}

The spring-boot-configuration-processor can only generate metadata for MetricsConfig but not AggregationConfig. Like this

Can spring-boot-configuration-processor generate metadata for AggregationConfig? by the way, this module should not include dependency 'spring-boot', so I cannot use @NestedConfigurationProperty