Did they even read it?

The movie 'Preadators' opens this July, it's the 4th (?) installment of the franchise. This is the movie poster for it:

 
 
 
 
 
 
 
 
 
 
 
 

Image - moviefone.com (click to enlarge)
 

The tagline caught my attention, it says:

"They are the most dangerous killers on the planet.

But this is not our planet."

I'm no english major, but this doesn't appear correct. Shouldn't it be:

"They are the most dangerous killers on THEIR/OUR planet.

But this is not THEIR/OUR planet."

or, even better:

"They are the most dangerous killers on EARTH.

But this is not EARTH."

If I'm right, how does something like this get passed and approved? Does it speak to the quality of the movie itself? Only time will tell...