Not in this case. If the long term identity is transferred from device to device there is no extra risk to trade off. It is like copying your PGP private keys

Not in this case. If the long term identity is transferred from device to device there is no extra risk to trade off. It is like copying your PGP private keys from one device to another. The associated public keys are still in your correspondents key stores, certified or not. Nothing changes for them and there is no reason for them to know what you have done. There is nothing here for Signal to do. Their issue is is the one that everyone who creates an encrypted E2EE messenger faces. There is no good analogy for cryptographic identities. So it is hard to produce a good conceptual model that the user can use to understand what they should expect and how they should react.