I don't think it's anything new. When I hiked in 1991, there was a small contingent of people who seemed mostly to show up in the towns and present themselves as thru hikers so as to claim some of the kindnesses, food donations, cheap or free beds, etc. that thru hikers benefit from. They never seemed to hike much. There were also some folks who I think were basically shelter squatters -- guys who would set up in a shelter for weeks at a time, sort of claiming to be a thru-hiker as a part of their act to cadge food handouts and so forth.
There's a certain quotient of sleaziness in the world, and the AT is not immune.