@Quirriff No, you misunderstood the meaning of the words.
Example: You want to look for shoujo fantasy manga, no romance or tragedy.
Included tags: Shoujo, Fantasy
Excluded tags: Romance, Tragedy
If both Inclusion and Exclusion is set to AND: it will show results with Shoujo Fantasy series that don't have both Romance
and Tragedy tags. But will still show Shoujo Fantasy Romance or Shoujo Fantasy Tragedy
Inclusion AND + exclusion OR: strictly Shoujo Fantasy only, NO Shoujo Fantasy Romance
or Shoujo Fantasy Tragedy
Does that make sense?