diff returns incorrect value when items are deleted

[karrtikiyer]

diff({'a': 1, 'b': 2}, {}, syntax='symmetric')
I expect the above to return
{delete: {'a': 1, 'b': 2}}
instead it returns
[{'a': 1, 'b': 2}, {}]

[Avraham David Gelbfish]

you probably want syntax='explicit'

[Jay R Bolton]

How about this?

diff({'a': 1, 'b': 2}, {}, syntax='explicit') == diff({}, {}, syntax='explicit')                              
> True

How could these two diffs be equivalent? Am I not understanding something basic here?