It seems that it would otherwise silently skip the rescan for pre-backup used keys that are still waiting to be generated into the keypool?

See also #11249 
{
    return RPCHelpMan{"listreceivedbyaddress",
                "\nList balances by receiving address.\n",
                {
                    {"minconf", RPCArg::Type::NUM, RPCArg::Default{1}, "The minimum number of confirmations before payments are included."},
                    {"include_empty", RPCArg::Type::BOOL, RPCArg::Default{false}, "Whether to include addresses that haven't received any payments."},
                    {"include_watchonly", RPCArg::Type::BOOL, RPCArg::DefaultHint{"true for watch-only wallets, otherwise false"}, "Whether to include watch-only addresses (see 'importaddress')"},
                    {"address_filter", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "If present and non-empty, only return information on this address."},
                    {"include_immature_coinbase", RPCArg::Type::BOOL, RPCArg::Default{false}, "Include immature coinbase transactions."},
                },
                RPCResult{
                    RPCResult::Type::ARR, "", "",
                    {
                        {RPCResult::Type::OBJ, "", "",
                        {
                            {RPCResult::Type::BOOL, "involvesWatchonly", true, "Only returns true if imported addresses were involved in transaction"},
                            {RPCResult::Type::STR, "address", "The receiving address"},
                            {RPCResult::Type::STR_AMOUNT, "amount", "The total amount in " + CURRENCY_UNIT + " received by the address"},