There is currently no way of distinguishing between a single element (e.g. $sxml->Result[0]) and a list of elements (e.g. $sxml->Result or $sxml->children()) which happens to include only one item. They can however behave differently - foreach ( $sxml->Result[0] as $result ) is equivalent to foreach ( $sxml->Result[0]->children() as $result ).
As far as I can see, there is no way of determining this with the current API. However, since the behaviour is different, the extension itself clearly tracks this distinction. It should probably be raised with the maintainers to add PHP access to this property for a future release.