If the bridge is grounded though, touching the strings will reduce noise. Hence the bridge is definitely grounded. If it weren't, touching the strings would have no effect at all. I would know, I've wired a guitar both ways.
And yeah, I know noise from not being shielded is the same touching the strings or not.
If he's only getting noise from sitting behind the guitar and not touching the strings there's nothing wrong with the wiring, there's just some kind of noise source in the room like lights or electrical wiring and if he shielded the guitar better he wouldn't even have to touch the strings to make the noise go away.
If you want the noise to go away even when you're not touching the strings, make sure all electronics are surrounded on all sides with grounded shielding tape. This will also go to reduce some noise that occurs even when you ARE touching the strings. This will NOT make the hum from single coils go away or noise that the amp already made by itself go away. Effects pedals and amplifiers pick up noise from the electrical outlets they're plugged into. You can't do much about the amp except make sure it's wired with good components, shielded wire, and the transformer wires are twisted. With effects pedals you can either get a better power supply or just use batteries, as batteries are DC already and have no inherent 50/60Hz AC hum.