I'm dubious about that advice. Years ago I lost equipment several times due to nearby lightning strikes, and eventually figured out that the probable reason was that I had ethernet wires running between machines that were powered from opposite sides of the 240V incoming power. A strike that hit just one of the two power wires could cause sufficient voltage differential to fry connected NICs (and, in some cases, adjacent parts on the motherboards). I believe I had UPSes or surge-suppressing power strips under all the gear, but that didn't help much for this because it was only clamping each power feed independently.
Eventually I made a rule that I wouldn't directly connect any gear that wasn't being fed from the same power circuit, falling back on wi-fi to connect clusters of gear on different circuits. I don't believe I lost any gear since then. (It might've helped that I also got a whole-house surge suppressor installed at the meter.)
Nowadays, instead of wi-fi links I make a point of installing an ethernet surge suppressor on any cable run between machines that are not on the same power circuit. I still insist on having a UPS powering any computer or network gear that I care about, but I've never seen problems from connecting multiple devices to the same UPS.
I do agree with trying to put your router more than 10cm from other gear. You probably don't need more than a meter's separation though --- remember radiated power falls off as the square of the distance.