No reason really as capacitors legs are rigid, but yeah, why not.
If I had to design an industrial wiring I would choose the one without the added wire, and on any other case (the real life 
) I’d prefer the one with the added wire.
Not very important tho.
I found this DiMarzio diagram which has a different switch but I think otherwise represents my guitar. I don’t see where a leg of the tone pot is grounded, just the body. What am I missing?
ETA link because it showed up see through on black background for me.
https://www.dimarzio.com/media/1465
Also I’ll just dump some pictures for more experienced troubleshooters to look at.
It’s kind of hard to see, but the white wire on the tone pot goes to the left terminal on the volume pot.
that’s the equivalent of the “added wire” wiring that we were talking about with @howard , also the same first wiring that I posted. One leg of the capacitor is grounded and the other leg goes to one leg of the tone pot. It works and it’s perfectly fine.
But in your case, if it doesn’t work (act like a volume pot) it’s because there is something wrong 
that’s what I was talking about : I think one of your tone pot leg is grounded where it shouldn’t. 20 seconds with the multimeter will bring you the answer.
Here I see that the “added wire” (the one between the tone pot and the volume pot) is a coaxial grounded wire. Totally useless and possibly the cause of the issue.
Top to bottom the resistance to ground is 9k, 9k, 480k.
no short circuit there 
it doesn’t help
It still might be shorting when it’s turned to playing position just not upside down on the work bench. I still think I’m going to just try electrical tape on anything that looks like it might short and see if it fixes it.
One thing that you could do is remove the tone cap from the circuit, and see if the tone pot (which would obviously not act as a tone pot without the cap) still acts as a volume knob, and still totally cuts the signal when set to zero.
If yes, there is a shortcut somewhere in the wiring. If no, you change the capacitor for a new one (any 22nF you can find) and it will most probably work.
very possibly a solution, yeah.
It looks to me like the unused leg on the tone pot is rotated in to contact with the shielding paint, which would do it.
And it looks like the reason for the coaxial wire is that’s how the pot bodies are grounded together. Agree it is likely superfluous.
Also, is the tone pot loose? It looks like it is in a different position in one of the pictures (almost touching on the cap side).
Yeah. I’m not sure if it was loose before I started but as I was turning the knob trying to see what resistance changed it moved. I guess tighten the tone pot so it’s not touching the cavity can be the very first thing I do.
oooh yeah ! very very possible !
On the plus side, it’s evidence the shielding is working 
Gold star! I haven’t put the cavity cover back on yet, but I held the pot in place centered and tightened the nut and now the tone pot is changing tone.
ETA: That makes me suspect the tone pot nut came loose from vibration and someone tightened the nut and turned the pot without realizing it.
Great ! @howard is officially a better electronic debugger than I am 
no
in this case, yes you’ve been right, looking where I wasn’t
Yes, those look like 6mm press-on knobs, should work. It looks like the shaft is compressed a bit, you might need to gently widen the gap.
Ah the old ‘someone’ else did it excuse. Man if I had a dollar for every time I’ve heard that on a job site 
Lol. I think it’s legit here though, I’ve had this guitar for 3 days of it’s 16 year life
