FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data. See About FME Rasters.
GeoTIFF files can be written with non-square pixel dimensions.
GeoTIFF supports rasters with an arbitrary number of bands, provided all bands are the same data type and no band has a palette. GeoTIFF also supports rasters with a single band that has a palette.