How do you have your writer setup? Removing an attribute in the AttributeManager only removes it from within the flow of the workspace. If you are using a template in your writer that still has those attributes, or the writer still contains those attributes, then they will be present in the file geodatabase with a <null> value. If you don't want those attributes present in the output, then you will need to remove them from the writer.
@fmemapper Now that you table is created, don't forget to Drop & Create...
Thank you @dustin and @Mark Stoakes . I thought that dropping and creating the table would update the fields and didn't realise that it was just updating in the workspace. Recreating the writer has now stopped the fields from showing.