Enabling Query Folding on Native Query

[SBIM]

I am trying to setup an incremental refresh but I am having trouble with the query folding. My connection is via an ODBC driver and I am connecting to an AS400 system. I can run queries against it fine, but I am getting the warning the M query may not support folding. I checked on the very first step and View Native Query was greyed out which is suppose to mean it does not support folding. So I have tried to follow some guides on how to enable it via a custom step in the Power Query Editor

e.g. 

= Value.NativeQuery(Source, "SELECT DISTINCT
OH.OHOTYP,
OHORDD,
OHENTD,
OH.""OHORD#"" AS ""OHORD#"",
OH.OHMTTM,
OH.OHCRQM,
OHREQD,
OH.OHINIT,
OH.OHDTMT,
OH.OHMTTM AS OHMTTM_1,
OH.OHMUSR,
OHP.OHCORD
FROM
IASP1.FRNDTA031.OH OH,
IASP1.FRNDTA031.O6 O6,
IASP1.FRNDTA031.CM1 CM1,
IASP1.FRNDTA031.O4 O4,
IASP1.FRNDTA031.OHP OHP
WHERE
OH.""OHORD#"" = O6.""O6ORD#""
AND OH.OHBTKY = CM1.C1STKY
AND OH.""OHORD#"" = O4.""O4ORD#""
AND OH.OHDRC = OHP.OHDRC
AND OH.""OHORD#"" = OHP.""OHORD#""
AND OH.OHLSUF = OHP.OHLSUF
AND (( OH.OHBTKY <> '007279'
AND OH.""OHORD#"" > 0))
AND OH.OHOTYP = 'SI'
AND OHP.OHCORD < 0
ORDER BY
5 DESC", null, [EnableFolding = true])

But I am getting the error Native queries are not supported by this value. Details: [Table]

Am I doing something wrong or is query folding not going to be an option here?

[edhans]

Initially Value.NativeQuery only worked with PostGRE SQL, then SQL Server as well. More are being added - cannot find a good list - but pretty sure AS/400 via ODBC is not yet on that list unfortunately.