Well gee, Keg, scales can be off as well. It you don't tare your scale, it can be off. If you don't hoist your hog fully off the ground the measurement can be off. So if you don't actually do things right, you can be off, regardless of the method.
Scorch hasn't been to Horn Hill Range. The biological papers I cited are not by folks who have been there.
If you have some actual proof that it doesn't work other than your opinion, do let us know. So far, however, you haven't actually come up with anything.
http://www.jstor.org/pss/3798635
http://www.sciencedirect.com/science...1&searchtype=a
You have no basis to argue that heart girth is a poor method unless you can refute all the studies that have shown where it works and that have been doing so for the last several decades.