If you ever check out the Hangman's Daughter trilogy, they mention 17c blenders loading tobaccos down with syrupy Germanic candy stuff, the game the whole weight/tax issue.
yep! This is an old trick.. when I was a kid there were people in my town spraying that old brown 90's weed with ammonia to make the bags weigh more. I'd bet any time people are selling a product by weight, It crosses somebody's mind to increase the weight with something cheaper than the product you're selling. With as many people selling pipe tobacco.. there are at least a few running that scam.