If the current page is a Flow board, it will ignore the oldid parameter.

I think ideally it should still work, and:

1. If it points to an old Flow board, show it read-only.
2. If it points to other content, delegate to the normal view function and show it.

This is not high priority, since while the current behavior may be slightly confusing to power users, the Flow index.php View doesn't do anything bad like displaying the old board read-write. Still need to check if you can post to old board via API.