Unchecking checkboxes does not exclude actions from plan execution

This IMHO critical problem is pretty easy to reproduce:

1. Compute the plan.
2. Uncheck checkboxes at some actions, e. g. the whole "Main" subtree (as you don't usually really want the default pages like Help, Sandbox etc. to be nested into Main).
3. Execute the plan.

Expected result: Only the checked actions are performed.

Actual result: All the actions are performed.

This behavior is not only counterintuitive, but it also goes against the documentation page on XWiki.org that states:

Each action has a checkbox. Only checked actions will be performed. So if you notice some changes that you don't want to perform, you can easily uncheck them. When you uncheck an action, it also affects its children.

Workaround: Exclude every single space from the plan manually (while nested spaces / pages doesn't seem to be supported here).