I just tried here using FME 2017 and it works. Are you sure that your geometry column has been registered properly in PostGIS? Check that your table appears when you execute this:
SELECT *
FROM public.geometry_columns
Alternatively, you can cast your geometry column as e.g. WKB:
select id, ST_AsBinary(geom) as geom
from test
After the SQLCreator, insert a GeometryReplacer on the attribute "geom" using geometry type "OGC well known binary". Choose to remove the attribute to save memory, you probably don't need it anymore.
I work with FME(R) 2016.1.2.1 (20160929 - Build 16674 - WIN64) and my table appears correctly in public.geometry_columns with good attributes. More specifically it's when I add a join in the request that it loses the geometry : "SELECT test.geom
FROM test
INNER JOIN all ON test.id = all.id "