ByConity: Why INSERT VALUES queries cannot be auto forwarded from server to workers?

Currently, in InterpreterInsertQuery.cpp, the logic of forwarding INSERT query to workers is as following:

......
    StorageCnchMergeTree * cnch_merge_tree = dynamic_cast<StorageCnchMergeTree *>(table.get());
    /// Directly forward the query to cnch worker if select or infile
    if (getContext()->getServerType() == ServerType::cnch_server && (query.select || query.in_file) && cnch_merge_tree)
    {
        /// Handle the insert commit for insert select/infile case in cnch server.
        BlockInputStreamPtr in = cnch_merge_tree->writeInWorker(query_ptr, metadata_snapshot, getContext());

        bool enable_staging_area_for_write = settings.enable_staging_area_for_write;
        if (const auto * cnch_table = dynamic_cast<const StorageCnchMergeTree *>(table.get());
            cnch_table && metadata_snapshot->hasUniqueKey() && !enable_staging_area_for_write)
        {
            /// for unique table, insert select|infile is committed from worker side
            res.in = std::move(in);
        }
        else
        {
            auto txn = getContext()->getCurrentTransaction();
            txn->setMainTableUUID(table->getStorageUUID());
            res.in = std::make_shared<TransactionWrapperBlockInputStream>(in, std::move(txn));
        }
        return res;
    }

    BlockOutputStreams out_streams;
    ......

My questions:

1. Why we only forward INSERT SELECT or INSERT INFILE queries to workers here?
2. Is the design of not forwarding INSERT VALUES queries functionally difficult to implement, or would it cause performance issues?

Thank you very much.