I have the same issue identified within this question but whilst using the PostGIS Raster transformer (https://community.safe.com/s/question/0D54Q00008p86kRSAQ/postgis-loading-default-values-being-overwritten-by-nulls-in-feature-writer)

As suggested in the answer I downloaded the most recent Beta (FME(R) 2022.0.0.0 (20220323 - Build 22311 - WIN64) ) and gave it another try. Unfortunatley I still get an error when trying to write to my PostGIS raster table. The issue seems to be related to the columns with default values I am not trying to write to. FME seems to be attempting to write nulls to these columns.

Is the Advanced > Missing Attribute Behaviour functionality also going to be included within the raster writer or another way around this?

Error message from log:

2022-03-29 09:36:45| 1.6| 0.0|ERROR |Bulk copy failed on table 'prime_data.paleodem' using delimiter ':'. Error was 'ERROR: null value in column "changedetect_date" of relation "paleodem" violates not-null constraint

DETAIL: Failing row contains (2, 181, 92, 720, 360, 5.01, P:\\02_Building_content\\083_6___K_190L\\K_...'

The changedetect_date column is not listed in the raster writer transformer so should not have values written to it...