When clicking on a suggested block, we would expect the suggestion to be dropped next to the initially selected block so as to continue to flow of logic. The majority of the time, this is going to be in the same scope as the initially selected block. I.e., your suggested block should land in the same sub-diagram. However, the default behavior for a dropped block is to land inside the top-level diagram.
This is because the drop happens based on position alone inside Autocompleter.vi:
I think the default behavior should be corrected so that to drop the block in the same sub-diagram which can be achieved by modifying the use of New VI Object in the examples above (and inside Copy Block to VI.vi).