Whenever I try to create a superflat world with the mod enabled, it ends up with normal world generation. A more jarring issue is the fact that new chunks in pre-existing superflat worlds end up with regular generation, which led to a void world I had poured hours into having a deep cold ocean surrounding everything.

found out it's an issue with worldgen mods in general (at least on my end) after testing Terralith as well

This is specifically a Terralith issue. This shouldn't occur with Tectonic on its own.