Problem/Motivation
The 'not in' operator of the ModerationStateFilter uses an OR conjunction, so when more than one filter value is selected, the query reads 'not in VALUE1 OR not in VALUE2'. Since the moderation_state only has a single value, it's bound not to be in one of those, so the condition returns FALSE for all entities.
Proposed resolution
The 'not in' operator should use the 'AND' conjunction.