Cancel button: different behaviour based on selected tab?

I have a pop-up with a dataview with parameter Photo. In the dataview is tabcontainer with two tabs: tab 1 just has attributes of the Photo-object, tab 2 has information on its parent, an Activity-object. The pop-up has two buttons, a default Save button and a default Cancel button (note, these are outside of the tabcontainer).  If I click 'Cancel' when viewing tab 1, only the Photo is rolled back If I click 'Cancel' when viewing tab 2, both the Photo and the Activity are rolled back Is this expected behaviour (not for me obviously or I wouldnt have asked:))? I would not expect the Cancel button to behave differently depending on which tab you currently have opened.  
1 answers

My guess its due to the following;

A tab container is by default lazy loading. So when opening the popup page and not having viewed the second tab, the content of the second tab isn't loaded and thus won't be rolled-back.

To test my assumption; open popup, open tab 2, switch back to 1 (tab 2 content is loaded) and execute cancel. If I'm correct, then the Activity will be rolled-back.

p.s. A tab in a popup???