Then why don't you go around, blast an ocean and send a planet into total homeostasis loss, and destroy the environment and everything?

These terraformers will do what another might do in a month in a single day. And the spores aren't for growing stuff; they're more for bacteria and the like to turn it to a Seeder-friendly environment.

Take a septic tank. You put chemicals in to help break down the bad stuff; this is what the bacteria is doing. It's taking all the bad stuff and breaking it down to good stuff.