Executing VBO programmatically + Rule sets: 'Operation arguments' box doesn't forward arguments

When using rule sets as an action in VBO, and the rule set has more than one argument, there are options to fill in the operation arguments.

If using the action to execute a VBO programmatically, there are as usual the textareas for setting the operation arguments. But there is also a box for setting *all* operation arguments, put together in an array.

This final box doesn't seem to work.

My test case:
1. A rule set 'double' that takes two arguments, say content + user.
2. A single rule and a single action in 'double', printing the message "node: [node:title], user: [user:user]".
3. Modifying the view admin_content so it can call the 'double' action.
4. A rule triggering on content save, using the updated node to execute a VBO programmatically.
5. The action calls the admin_content (overridden) view, with the action double.
6. In the box 'operation arguments', enter return array('node' => node_load(1), 'user' => user_load(1));.
7. Create a new content.

The rule will call the double action for every node on the site, and should display the title for node 1 and name for user 1. It displays no node and user name 'Anonymous', indicating that the operation arguments were not forwarded.

Suspecting that the difficulties may lie in putting an object inside the array, I also tried returning NID and UID.
Also tried creating a rule set that takes two strings as arguments, and using the settings return array('string1' => 'alpha', 'string2' => 'beta');.
Same effect -- nothing seems to reach the VBO.

This isn't a big deal, since the ordinary boxes for operation arguments works just fine. But I thought I should report it anyway.