Yes that’s exactly right. XInput controllers are enumerated both by direct input and XInput so if there wasn’t some kind of filtering out on the direct input side you would control 2 players in the game. Hopefully your attempt to “not listen to XInput” will disable the filtering as well.
The first version of Defend the night worked with 8 XInput controllers but the controllers were a bit too sensitive so some additional dead zone needed to be added. Hope this is a clue to get it working again.