Something like it.
Here's another reference:
This is IMO the key illustration from that document:
The safety ground shown above as one wire above may actually be a network of wiries in an actual home. It is formed of the (usually green insulated or uninsulated) safety ground wiring related to the grounding pin on modern electrical outputs. Typically, there is a continuous (but spliced and tapped) piece of copper from the outlet back to the distribution panel, and the safety ground on the distribution panel is connected to a ground rod driven into the earth or something like it.
The amount of current flowing in this wire should be zero or just leakage current, but sometimes it is actually quite a bit. The gauge of this wire is usually the gauge of your house wiring, in the US either 12 or 14 gauge. The advice to connect the two chassis with a piece of wire basically puts that wire in parallel with a 12 or 14 gauge wire, and given the good conductivity of 12 or 14 gauge wire you aren't going to improve on it very much! You can improve on it if it is defective.
I've measured as much as several volts difference between safety grounds in different parts of the same building. This will make unbalanced lines hum like a thousand bees! Most modern balanced inputs are active circuits which lack the ability to reject high ground potential differences. Transformers and optical fiber are nearly perfect at rejecting hum from this source.
The source you cited shows a lot of frequency response losses due to transformers that are not cheap. I'm surprised! I'm most familiar with the RS transformer which actually has better response than the high priced ones. My own measurements show even better performance. But the author has tapped into one undeniable truth and that is the fact that the RS transformer picks up hum fields very strongly. I have one in the signal path to my subwoofer, and it didn't stop humming until I placed it inside a small tomato paste can, with the top replaced with a jar lid that just happened to slip in nice and tight.