They should have gone all in originally and just named it the "Committee for Internal Security".
I was also surprised at the time by often seeing "Department of Defense", as we were bunker busting and daisy cutting the crap out of people across the globe. I also just recently learned that we don't know the number of US military installations around the globe (700?, 900?) and instead of dismantling them after collapse of USSR, we found new justifications.
The more traditional phrase, Republic, used by Benjamin Franklin, and in the pledge of Allegiance is, as your article points out, more closely ties the U.S. to certain philosophical principles, whereas the term homeland is restricted to the physical, geographic location and the individuals in it.
If the lexicon is reduced to physical protection, than it's less vulnerable to arguments of lost liberty.