Really? Because when H and L flank it, it suppresses the ground field. It isn't perfect because the inductance is mediocre, but not everyone can afford $50/ft on top of tearing up all their walls.
Unfortunately I do not have the article with all the measurements with me. But for minimal magnetically induced noise we should have a a twisted L-N pair with a ground wire not too close. Twisting the three wires, as some people do, is not desirable.
While I look for the complete paper please see: http://www.johnlsayers.com/phpBB2/viewtopic.php?f=16&t=19656 . I quote from it:
"To minimize induction of noise into the ground wire, there are two strategies: 1. Because, at any instant in time they carry the same current in opposite directions, put these two wires as close to each other as possible so their magnetic fields neutralize/cancel each other. Tight twisting is the most practical way to do this; and 2. Put the “victim” ground wire as far away as possible from the current-carrying pair. Because the magnetic fields are very intense close to this pair, the closer the ground wire gets to them, the more critical its exact positioning becomes"