OBJECT_INNER_PAIRS description unclear

The description of OBJECT_INNER_PAIRS doesn't make sense to me. I think I grasp what it does — explode an object into an array of key/value pairs — but the docs say a lot of things that seem to contradict that or just confuse the matter.

"Similar to an INNER JOIN operation, this function returns only the documents for which the parent has a relationship with a child." — No indication of what 'parent' and 'child' are; also, this function doesn't return documents. The explanation doesn't shed any light on how the function behaves.

"This function is particularly useful when the argument is an array" — This function operates on an object (aka dictionary or map), not an array. I don't understand what it could do with an array, since an array doesn't have keys. If it does operate on arrays, the docs need to spell out what it does to them.

"Arguments: expression: Valid strings or arrays." — How can it be a string? And what about being an object, which seems like the default?

"Return Value: An array of values or name-value pairs in N1QL collation order and only the documents for which the parent has a relationship with a child." — Again the "only the documents..." part doesn't make any sense to me.