I think their policy used to be 30 days (or maybe longer) but at some point this was silently changed to 20 days. I’m not sure why the change was made but @r10s gave the cryptic answer:
But because I’m not a law expert, I don’t understand why 20 days is any different to 30 days regarding GDPR and I’d love to get some clarification for this.
This is very puzzling. Do both your devices show that you have the same fingerprint?
Not if your device is aware of a possible second device!
Maybe if you make a backup and then redo the addition of the second device, this could solve the issue? But then we might never know what caused the problem.