With jdk-12-ea+22 (but not jdk-12-ea+21) I see:

javac -Xdoclint:all ArraySerialField.java
ArraySerialField.java:3: error: array type not allowed here
    /** @serialField longs Long[] the longs */

---

/** Obdoc. */
public class ArraySerialField {
    /** @serialField longs Long[] the longs */
    private static final java.io.ObjectStreamField[] serialPersistentFields = {
        new java.io.ObjectStreamField("longs", Long[].class),
    };
}