Hm… I doubt that was intentional; possibly the wrong thread was deleted by accident during de-duplication.
In general, you can copy volumes to a different region using fly vol fork --region.
Once you have a volume in the region you want, the following classic post is the easiest way to get a Legacy Postgres cluster up and running again:
https://community.fly.io/t/urgency-problems-with-postgres-the-database-is-not-responding/19926/2
(If the original database was created a while ago, then you may also need an explicit --image-ref.)
I tried this in ewr → iad while drafting a reply in your other thread and didn’t encounter any problems…