As JAR outlines, it includes language used to separate the responsibility of the ball first hitting OB a player and a non-player.
The statement is well-worded, but does usually prompt a question from many people when read. (I've had a coach before ask me about this one.)
BadNewsRef's statement isn't irrelevant because by including the fact that the ball hit the floor, it "completes the circuit" (think electricity) of when a ball must becomes dead. It just so happens that a player was OB and the ball hit them first.
I have found in the years that I've trained guys, what might first go through someone's mind, that the ball hitting the floor means the ball is OB, but then they realize that A1 was OB and therefore the ball was already dead. Then they realize that they (but shouldn't) wait for the ball to hit the floor before blowing the whistle and stopping the clock.
I understand that newbies that do this might not be at Nevada's skill level yet.
The opposite, and similar way of thinking is when A1 inbounds to A2, but with pressure from B1. The pass is tipped by B1. I know that there are guys in every area that wait for the ball to be touched by A2 before chopping in time. I've seen it all over my fair province of Ontario and I believe it happens elsewhere too. (Not by me though.
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