What is up with Sonic Frontier's boss names?

I genuinely can't find a theme. At first glance it looks like they're named after creatures, as Squid, Spider, Wyvern, etc. All fit perfectly based of their behavior and appearance, but then others are named after combat stuff like Ninja, Shinobi, Knight, and Sumo, so it seems like they're named after what they look/act like which is further reinforced by "tower", but then there's the anomaly of "fortress", which could be overlooked but then they just say random bullsh*t go with the giant creature named Asura?? a spiky tower named strider??? Giganto?!?!? What's going on here?