I just double-checked to see if that behaviour had changed since I stopped cross-posting. It has not. If you edit a post on DW that has access set to "Everyone", your LJ post will be updated to have the same level of access.

ETA: The coding to change this has been written but has not been committed. Expect the behaviour to change at some point in the future. dw_news publishes the link to codes committed if you want to watch for when it goes into effect.