I tend to agree with you on this, that is a stretch. I know some of the dogs that were shaven had rough, long wavy hair. I'd lean more to what Gotap_d said 3-5 oz. just based on pure common sense. I've never weighed the hair to make a 100% factual statement though.
I personally have never been so technical to need every ounce of weight to use as an advantage. I was never in that lane and never will be. But I know men who were in their day and it is fascinating to discuss their methods of gaining even the smallest of advantages, whether scientifically or just in their mind.
S_B