selection and grouping/reduce ordering

The documentation says that the selection (for instance function key) is applied after the reduce function. Why do I get the following results ?

If I have the documents :

and the map is : emit([doc.k1, doc.k2], null)

and the reduce is: _count

why do I get the following results ?
query.group_level(1).key(1) = 0 // expected 2
query.group_level(1).key([1,1]) = 1 // expected 0

It seems that key is applied before the grouping/reduce function. If you execute query.group_level(1), you got a single result :
[1] => 2

If you add .key(xxx), the data set of the views seems to be filtered to match only the key xxx.
if xxx=1, there is no result because there is no row in the view with the key 1.
if xxx=[1,1] there is a single result because there is a single row with the key [1,1]

Is there something wrong in my tests ?