My late wife grew up partly on her grandparents' tobacco farm near Dover, N.C. Part of her participation in tobacco farming was a task called "sticking tobacco," which meant using twine to tie the stems of the harvested leaves in bundles together to hang on sticks in the tobacco barn to cure with fires at the base of the barn.
I'm surprised that any of this twine would end up in the product. It's easy to see how it would happen, but it seems like the blenders have every motive to keep it from happening.
But yes, twine is definitely part of the process and could easily end up in the blend if processing isn't meticulous.
My late wife had many good tales about the farm, including about a small family graveyard from previous ownership from which the dogs would drag out Mr. "Smith's" skull (I can't remember the actual name) every year or two, and someone would have to put it back in the ground. Lots of jack'o'lanterns went on the graves at Halloween.