If you're an e-nerd, you know that a "proxy" is something, as in software or hardware, that blocks your IP address. While keeping that in mind, I also draw from it's denotative meaning. I use the word as connotation whenever information from a first object of person (or dampened in this case) and then falsely represented by a second person or object to a third person or object. Now apply that to the situation in this case, body to pickgaurd, pickgard to mounting screws then pickups.
Anyways, this is a forum. It's on the internet. Oh god what are we going to do? Learn to accept small amounts of connotation and that words have multiple denotative meanings or call the grammar police.
Alright then, because it has a mind and it can clearly make a thought and say to itself "Oh, I don't care" ... imagine this.
A pickup is vibrating exactly in harmony with a string. It follows it's movement exactly. How the heck is it going to create a tone? Now, this is an exaggeration. But in practicality, try vibrating a pickup in front of oh, let's just say an iron nail... it's going to create a current. Don't forget your ground. Depending on the speed of the vibration, it will create a signal that is perceivable.
The magnets within the pickup create an electromagnetic field. When the pickup is moved, so is the field. I'd go deeper, but I think you're intelligent enough to figure out this 101 stuff.
Now the real problem I made in the post was to say that a pickgaurd is going to make a huge difference. I didn't actually intend on creating this premise that "Oh pickgaurd suck, they kill your tone." Why? They don't. They add character.
Another problem with measuring tone difference between guitars is your amp and accessories. First, turn the tone pots all the way down. If you love to play with distortion, quit worrying about hearing a tone difference. Most of this tone stuff is for peeps who play clean into a tube amp, and only model their tone to compensate for 60-cycle.