R dbWriteTable to Cloud Spanner requiring column names - r

Question

I'm trying to insert data into a Cloud Spanner table using DBI's dbWriteTable in R, however, it is asking me to supply column names. It is my understanding that as long as the dataframe contains the same amount of columns as required by the table then this should work. Here's my code and error I'm facing (leaving out connection details):
Code:
write.to.spanner <- function(table, df){
dbWriteTable(con, table, df, overwrite=FALSE, append=TRUE, row.names=FALSE)
}
req_df <- data.frame(req_id=123, req_name="test req")
write.to.spanner("dbi_test", req_df)
DDL for spanner table:
CREATE TABLE dbi_test (
req_id INT64,
req_name STRING(20),
) PRIMARY KEY(req_id);
Error:
Warning: Error in .local: execute JDBC update query failed in dbSendUpdate ([Simba][SpannerJDBCDriver](100605) There was an error while executing the DML query : INVALID_ARGUMENT: com.simba.cloudspanner.shaded.com.google.api.gax.rpc.InvalidArgumentException: com.simba.cloudspanner.shaded.io.grpc.StatusRuntimeException: INVALID_ARGUMENT: INSERT must specify a column list [at 1:1]
INSERT INTO dbi_test VALUES(#var1,#var2)
I'm able to insert using dbSendUpdate but would prefer to use dbWriteTable and not write out insert statements.
This works fine:
write.to.spanner <- function(table, df){
insert_qry <- paste0("INSERT INTO ",table," (req_id, req_name) VALUES (",df[1,1],",'",df[1,2],"');")
dbSendUpdate(con,insert_qry)
}