As far as I have always known, you could only indicate resource locations by using a ghost shell (or the discontinued Scout reports that Cayde used to sell) for that particular destination..
I don't have the dreaming City Ghost shell which I think you can only get in the Last Wish raid?
If anyone has an answer for this I'd love to understand what is going on here
Edit: I'm a Striker Titan and so therefore couldn't possibly be making use of the Hunter's Nightstalker resource detector, none of my ghost shells can be used in the Dreaming City and none of them are from the haunted forest *shrug* so odd...
Edit #2: Case closed! Our community friend, @cdfa1only, revealed to me that I have an active perk on my clan banner which grants additional resources in (the reef) Tangled Shore AND the Dreaming City.
Thank you cdfa1only!