Why is Collections.addAll supposed to be faster than c.addAll

The Java API docs say the following about Collections.addAll

The behavior of this convenience method is identical to that of c.addAll(Arrays.asList(elements)), but this method is likely to run significantly faster under most implementations.

So if I understand correctly, a) is slower than b):

a)

Collection<Integer> col = new ArrayList<Integer>();
col.addAll(Arrays.asList(1, 2, 3, 4, 5));

b)

Collection<Integer> col = new ArrayList<Integer>();
// Collections.addAll(col, Arrays.asList(1, 2, 3, 4, 5)); <-- won't compile
Collections.addAll(col, 1, 2, 3, 4, 5);

Can anyone explain to me, why that is?

edited: corrected code example. thx to polygenelubricants