Brunei isn't on the Bertelsmann because it is small (<1 million people), not because of its political structure.
The EDI explicitly does not try to asses whether a country is democratic or not, but just allows relative comparisons. It also doesn't include smaller countries but doesn't have as clear of a cutoff.
If you are going to use inclusion on one or more of these lists as an argument, you'll have actually cite where those lists use status as a democracy as a criteria for inclusion and how that is assessed.
The EDI explicitly does not try to asses whether a country is democratic or not, but just allows relative comparisons. It also doesn't include smaller countries but doesn't have as clear of a cutoff.
If you are going to use inclusion on one or more of these lists as an argument, you'll have actually cite where those lists use status as a democracy as a criteria for inclusion and how that is assessed.