Why does dplyr::tbl wrap a CTE in a subquery for SQL Server dbb's but not for RSQLite?

[Bertusian]

Hi,

The T-SQL (a Common Table Expression) here mentioned runs well in SSMS.

WITH 
  a AS
  (
    SELECT 'a' AS genus, 1 AS taxa
    UNION ALL
    SELECT 'b' AS genus, 1 AS taxa
    UNION ALL
    SELECT 'c' AS genus, 2 AS taxa
    UNION ALL
    SELECT 'd' AS genus, 1 AS taxa
    UNION ALL
    SELECT 'e' AS genus, 2 AS taxa
    UNION ALL
    SELECT 'f' AS genus, 3 AS taxa
  ),
  b AS
  (
    SELECT 'a' AS genus, 1 AS code
    UNION ALL
    SELECT 'a' AS genus, 2 AS code
    UNION ALL
    SELECT 'b' AS genus, 1 AS code
    UNION ALL
    SELECT 'b' AS genus, 2 AS code
    UNION ALL
    SELECT 'c' AS genus, 3 AS code
  ),
  c AS 
  (
  SELECT a.genus, taxa, code
  FROM a 
    LEFT OUTER JOIN b ON a.genus = b.genus
  )
SELECT genus, taxa, code
FROM c

When connected to an SQLIte dbb I manage to read in this CTE as a remote tibble with the following code.

sql2 <- readr::read_file("sql/WITH2.sql")
(test1 <- dplyr::tbl(con, dplyr::sql(sql2)))

However, when trying the same when connected to SQL Server dbb, the code gives an error because the tbl function then wraps the WITH statement in a subquery, which is doesn't when trying the same on an SQLite dbb. How can I prevent tbl wrapping the CTE in a subquery?
The following error makes clear what tbl is doing when connected to SQL Server.

Error: nanodbc/nanodbc.cpp:1617: 42000: [Microsoft][ODBC SQL Server Driver][SQL Server]Incorrect syntax near the keyword 'WITH'.  [Microsoft][ODBC SQL Server Driver][SQL Server]Incorrect syntax near the keyword 'with'. If this statement is a common table expression, an xmlnamespaces clause or a change tracking context clause, the previous statement must be terminated with a semicolon.  [Microsoft][ODBC SQL Server Driver][SQL Server]Incorrect syntax near ','.  [Microsoft][ODBC SQL Server Driver][SQL Server]Incorrect syntax near ','.  [Microsoft][ODBC SQL Server Driver][SQL Server]Incorrect syntax near ')'.  [Microsoft][ODBC SQL Server Driver][SQL Server]Statement(s) could not be prepared. 

<SQL> 'SELECT *
FROM (WITH 
  a AS
  (
    SELECT 'a' AS genus, 1 AS taxa
    UNION ALL
    SELECT 'b' AS genus, 1 AS taxa
    UNION ALL
    SELECT 'c' AS genus, 2 AS taxa
    UNION ALL
    SELECT 'd' AS genus, 1 AS taxa
    UNION ALL
    SELECT 'e' AS genus, 2 AS taxa
    UNION ALL

Grateful for any help!