Someone didn't read Neal Stephenson's book.
Seveneves was a fun book!
The comparison would be Orson Scott Card writing Ender's Game to set up the universe of Speaker for the Dead, but instead making Speaker for the Dead a third of its size and calling it the last few chapters of Ender's Game. They should just be different works in the same setting.
I loved them both.
But the moon has handled much bigger collisions without a single fatality!