If you look at the photos, you’ll notice that the rainfly arcs up at each end of the tent. This saves a bit on weight and improves ventilation, but it was one area that worried me when I reviewed the 3-person version years ago. Thankfully this has never been an issue, the bathtub floor (which is what is exposed below the fly) has proved plenty waterproof in my use.
Speaking of bathtub floors, there is a clip-in vestibule floor that’s also a bathtub shape. Nemo calls this the Landing Zone. It’s a little extra triangle of fabric that covers about half the vestibule and protects any gear you’ve stored there