I think you want them to be separate so you can take them out individually and clean them particularly if there is water on the bottom or snow or dirt.
2016 - 535I X with M Sport 9/10
2013- 335i X Delivered 10/31 - Halloween Treat! Sold 9/10
2008 - Champagne colored 328i X - sold 10/19/12
2005 - 325i X Silver Bullet, gone but not forgotten
2016 - Jeep Grand Cherokee Summit - Diesel