Don't know if this is a regression, but when I create a new document with Prefer Linked, then place an image, it comes in embedded according to Resource manager. Document setup confirms Prefer Linked was selected correctly.
Replace image from context bar, and clicking the new Options, then prefer linked DOES work correctly.
I've also tried starting as embedded and switching to linked in Document setup - same result. I've restarted AD from first launch just in case, no change.