Ah. I suspected as much (I wondered if fly ips list had been added for showing outgoing IPs as I’ve not used that command before. But it seems not, as you confirm it returns the IP the DNS points to).
So … that’s a known issue unfortunately. You will see other people asking about it, for firewall/whitelists. You could ask someone like @kurt for an outgoing IP range from your app’s region (which you could then whitelist) else perhaps use Google’s proxy which seems designed to solve this issue? About the Cloud SQL Auth Proxy | Cloud SQL for MySQL | Google Cloud
The downside of asking Fly for their IP/range is they change: