That's not accurate. My VII does 4.59 at 160 watts on Grin29. Sounds to me to be more efficient.
I think your post is the not accurate one. He said it was ONE of the most efficient chips, not THE most efficient. He was speaking from an affordability standpoint.
Buying a Radeon VII for mining is incredibly stupid for a number of reasons...the primary one being the cost. Buying one at all really isnt a great idea since NVIDIA cards are better in almost all gaming aspects as well.
P.S. My 2 year old ALREADY paid for GTX 1070s run about 4.1-4.2gps @ 150w without being $700 in the hole per card.....