Specifically, it adds an address into the wallet.

Easy to test now thanks to https://github.com/bitcoin/bitcoin/pull/14410
```
diff --git a/test/functional/wallet_importmulti.py b/test/functional/wallet_importmulti.py
index 9ba6860..bff37b2 100755
--- a/test/functional/wallet_importmulti.py
+++ b/test/functional/wallet_importmulti.py
@@ -95,6 +95,7 @@ class ImportMultiTest(BitcoinTestFramework):
         assert_equal(address_assert['iswatchonly'], True)
         assert_equal(address_assert['ismine'], False)
         assert_equal(address_assert['timestamp'], timestamp)
+        assert_equal(address_assert['ischange'], True)
 
         # ScriptPubKey + internal + label
         self.log.info("Should not allow a label to be specified when internal is true")
```

if (scannedTime <= GetImportTimestamp(request, now) || results.at(i).exists("error")) {
                    response.push_back(results.at(i));
                } else {
                    UniValue result = UniValue(UniValue::VOBJ);
                    result.pushKV("success", UniValue(false));
                    result.pushKV(
                        "error",
                        JSONRPCError(
                            RPC_MISC_ERROR,
                            strprintf("Rescan failed for key with creation timestamp %d. There was an error reading a "
                                      "block from time %d, which is after or within %d seconds of key creation, and "
                                      "could contain transactions pertaining to the key. As a result, transactions "
                                      "and coins using this key may not appear in the wallet. This error could be "
                                      "caused by pruning or data corruption (see bitcoind log for details) and could "
                                      "be dealt with by downloading and rescanning the relevant blocks (see -reindex "
                                      "and -rescan options).",
                                GetImportTimestamp(request, now), scannedTime - TIMESTAMP_WINDOW - 1, TIMESTAMP_WINDOW)));
                    response.push_back(std::move(result));
                }
                ++i;
            }
        }
    }
    return response;
}