The 09+ don't run the water pump off the timing belt unlike the first gens, but off the serpentine belt instead. This means it can be changed independently of a timing belt job.
However, changing it still requires the motor mount to be taken off, which will be off when the timing belt is replaced anyway. This makes it a "may as well change it since it's convenient" type of item, unlike the potential disaster on the older models if it's pulley broke
Exactly! The word "convenient" is an understatement.
It's a case of "may as well change everything that's in there, since it's a labor intensive job, and it will be a time consuming and expensive PITA if you have to open it up a second time."