Here is the part I got confused first Urashiki tells Toneri they saw it all and then says we don’t know anything about Earth. I think what Urashiki could be referring to is the same 16° curvature Kinshiki noticed.
The planet itself might be unique for it to have to abnormal curvature rating. Or maybe there are some events that happened in the past 1000 years that they didn’t know of. It could be both.
When Urashiki tells him that more than one of them were dispatched, Toneri seemed to be surprised and it meant that he doesn’t know about Momoshiki and Kinshiki. Urashiki tells him that he isn’t authorised to kill a clan mate. Instead Urashiki drops a box that Toneri recognized as a time freeze. It won’t kill, instead, Urashiki tells him to enjoy the palace of the dragon king for the next 10,000 years. Not too much is know about the mechanics of time stop, but 10,000 years is a long time. Unless someone saves him, we might not be seeing Toneri for a while.