Wrong implementation of Oracle Java ConcurrentHashMap?

I am testing ConcurrentHashMap on Oracle's Java 8 implementation:

ConcurrentMap<String, String> concurrentMap = new ConcurrentHashMap<>();
String result = concurrentMap.computeIfAbsent("A", k -> "B");
System.out.println(result);  // "B"
result = concurrentMap.putIfAbsent("AA", "BB");
System.out.println(result);  // null

The Javadoc of computeIfAbsent does say that

Implementation Requirements:

The default implementation is equivalent to the following steps for this map, then returning the current value or null if now absent:

if (map.get(key) == null) {
    V newValue = mappingFunction.apply(key);
    if (newValue != null)
        return map.putIfAbsent(key, newValue);
}

It said then returning the current value or null if now absent. So shouldn't it be returning null? Given that putIfAbsent is also returning null.

What am I missing here?