Right - I get it now! I think my awareness of the previous rules meant I was laboring under a mis-understanding.
"Anchors may be marked to falashback and activate an At Home scene at any time."
(Spotted a typo above, btw!)
I should have read fintcher's thread below more closely - apologies for my obtuseness.
From your playtesting, how did the flashbacks go in terms of potentially disrupting the flow of the horror? Like, you're at some climax to the story, and a PC who has a high stress marks an anchor and triggers a flashback to wandering fields of flowers with his girlfriend? Jarring or not?