### Elasticsearch Version

8.8.0-SNAPSHOT

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

MacOS

### Problem Description

API when called is returning invalid response, on the same data terms aggs query runs fine 

![image](https://user-images.githubusercontent.com/3505601/220749805-ddf0d735-60d5-4e45-85bf-941ea3076a3f.png)


When run as aggs query 

![image](https://user-images.githubusercontent.com/3505601/220764360-49f7b648-8b15-43cf-afe2-01bd62e8ebc5.png)


### Steps to Reproduce

Queries are mentioned above ^^

### Logs (if relevant)

_No response_
server/src/main/java/org/elasticsearch/index/mapper/flattened/FlattenedFieldMapper.java
public static final String CONTENT_TYPE = "flattened";
    private static final String KEYED_FIELD_SUFFIX = "._keyed";
    private static class Defaults {
        public static final int DEPTH_LIMIT = 20;
    }
    private static Builder builder(Mapper in) {
        return ((FlattenedFieldMapper) in).builder;
    }
    public static class Builder extends FieldMapper.Builder {
        final Parameter<Integer> depthLimit = Parameter.intParam(
            "depth_limit",
            true,
            m -> builder(m).depthLimit.get(),
            Defaults.DEPTH_LIMIT
        ).addValidator(v -> {
            if (v < 0) {
                throw new IllegalArgumentException("[depth_limit] must be positive, got [" + v + "]");
            }
        });
        private final Parameter<Boolean> indexed = Parameter.indexParam(m -> builder(m).indexed.get(), true);
        private final Parameter<Boolean> hasDocValues = Parameter.docValuesParam(m -> builder(m).hasDocValues.get(), true);
        private final Parameter<String> nullValue = Parameter.stringParam("null_value", false, m -> builder(m).nullValue.get(), null)
            .acceptsNull();
        private final Parameter<Boolean> eagerGlobalOrdinals = Parameter.boolParam(
            "eager_global_ordinals",
            true,
            m -> builder(m).eagerGlobalOrdinals.get(),
            false