Others please chip in too, but for me it's the "tummy time" she keeps pushing for unknown reasons. As others have mentioned, Ari is basically only a newborn when you correct her age for her prematurity. They don't really need tummy time this early cos they're still spending a lot of time being sleepy between feeds.
But when you do tummy time, you get on the floor with them so that if they face plant (because they don't have the strength and skill to move their huge heads) you can reposition them so they can breathe. Also you're on the floor with them so they can see Mum/Dad and interact with them.
You certainly don't plop them on the floor alone while your dog with overgrown claws stretches out by the kids head, while you sit in your wheelchair unable to assist in any fashion.