panic; Keep reading, the advantage is explained in the rest of that post, at least in my demented mind. During warmup (thermo. closed) there can be uneven temps in the head (for example where the temp guage sender is). The thermostat is heated only be convection as no water is yet circulating possibly leading to a faulty reading by the thermostat. With the 1/8" hole, a small amount of water will circulate, evening out any hot spots and bringing the head temperature to a more even heating that the thermostat can react to. In addition, if the old girl needs a good burp, she doesn't have to wait until the thermo opens.
Also, I'm thinkin' it can't be a good thing to have a 55-year-old cast-iron head a lot hotter at one end than at the other end, even if it's just for a few minutes.
