There's no need to playtest every rule. Sometimes you can tell by reading alone. Take the Slayer theme. I don't have to see it in play to know I don't like it. Sometimes you don't actually have to eat the dog poop to know it's gonna taste foul.
That's not the point of play testing. The point is to play the rules presented and then answer the specific survey questions about it. That feedback is then used to develop the game. If you haven't played the system as presented, you can't answer the questions honestly, and posting on a forum "I didn't like the look of the play test material so I changed it" isn't feedback in any meaningful sense.
A play test is a two-way thing; it carries an obligation. It's not a free gift. Sure, you can ignore that and just play the thing as a free game and change it about how you like, and nobody can stop you, but let's not pretend you're play testing at that point.