Following Teiid query:

SELECT TimeStampValue, LOWER(TimeStampValue) FROM BQT1.SmallA

is pushed as:

SELECT g_0."timestampvalue" AS c_0, lcase(stuff(stuff(convert(varchar, g_0."timestampvalue", 102), 5, 1, '-'), 8, 1, '-')+convert(varchar, g_0."timestampvalue", 8)) AS c_1 FROM "bqt-server"."dvqe"."SmallA" AS g_0

and returns the string representation of timestamp as:
2000-01-0100:00:00
2000-01-0100:00:01
...
Notice the missing space between date and time part.

SAP IQ is capable of converting the value implicitly, e.g. when I issue query

SELECT TimeStampValue, LOWER(TimeStampValue) FROM SmallA

directly against SAP IQ instance, I get following string format:
2000-01-01 00:00:00.000
2000-01-01 00:00:01.000
....

The same results are returned if I use an explicit convert like:

SELECT TimeStampValue, LOWER(CONVERT(varchar,TimeStampValue,121)) FROM SmallA

For more formatting options see SyBooks Online