HR, I'm not sure what you're confused about but I think it might be the definition of "catch." You're thinking of the touch and grab as the catch, the physical act of securing the ball by the receiver which can be done on the ground, in the air, in the endzone, etc. The Rules Book is referring to its definition of a catch that includes the touch and grab, but also returning to the ground inbounds with possession. A hit before the touch could be pass interference, but a hit after the touch that prevents the receiver from landing inbounds is not. It is, however, a hit that happens before the catch.
I think this change makes is far less likely that a judgment call will determine anything.
This post was edited on 8/15 5:49 PM by White hat