[`Setting.versionSetting`](https://github.com/elastic/elasticsearch/blob/0652a5915586abbcdfdfffa91a391740f0147752/server/src/main/java/org/elasticsearch/common/settings/Setting.java#L1275) (only used by index compatibility setting) does not use the `Validator` passed in - its just discarded. Looks like it's been like this since it was introduced by https://github.com/elastic/elasticsearch/pull/83264 in 8.2.0.

Enabling this causes some tests to fail. Enabling this may cause problems for indexes that have a wonky setting already applied.
server/src/main/java/org/elasticsearch/common/settings/Setting.java
public SimpleKey toConcreteKey(String missingPart) {
            StringBuilder key = new StringBuilder();
            if (prefix != null) {
                key.append(prefix);
            }
            key.append(missingPart);
            if (suffix != null) {
                key.append(".");
                key.append(suffix);
            }
            return new SimpleKey(key.toString());
        }
        @Override
        public String toString() {
            return keyString;
        }
        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            AffixKey that = (AffixKey) o;
            return Objects.equals(prefix, that.prefix) && Objects.equals(suffix, that.suffix);
        }
        @Override
        public int hashCode() {
            return Objects.hash(prefix, suffix);
        }
    }
}