Interesting. I haven't run a pruned wallet yet, and I didn't realize that you couldn't start a new wallet with a pruned blockchain.
It applies for importing private keys as well.
ranochigo states that "the client cannot accurately obtain all the transactions related to your wallet", but if its a new wallet then there shouldn't be any transactions related to the wallet yet.
Additionally, doesn't a pruned node still keep the full UTXO? If so, it should still be able to figure out which unspent transaction outputs are yours.
To my understanding, Bitcoin Core automatically assumes the addresses that were imported in after or during the synchronization to have transactions associated with it already. This applies for the changing of wallet.dat.
They do.
They can compute the balance of the address but they cannot get all the transactions related to the address since the blockchain is pruned. Even though it is possible for users to spend their Bitcoin, they cannot see the history of the transaction beyond the point of time when it was imported. That is probably the main reason why they force a reindex.It would be helpful for users to indicate if the address have transaction before the point of Blockchain prune but it may complicate things for the user if they don't understand it.