Even with an extra border, instances created at runtime are beeing deleted right after they got created if they were placed outside of the screen but within the extra border.
This doesn't apply to instances that were placed in the scene editor before starting the game.
Steps to reproduce the behavior:

Additional border is per instance, it's not a global setting. So you have to apply it to objects that you create
To avoid this confusion, I think having the additional border in the settings of the behavior would help. You can create a card for it on trello if you wish
Thanks for clarification ... Done:
https://trello.com/c/77rCdzuA/253-show-additional-border-property-in-the-behavior-editor-of-destroy-outside