I think the difference between a model aircraft and a "drone" is line-of-sight visual control vs some sort of GPS, satelite, or cellular control system that extends the range beyond visual.
The other key difference is SIZE. In the past, "drones" were full size airplanes retrofitted with radio control. Model airplanes were small machines less than 5 kg in mass with a wingspan less than 2 meters. Unfortunately real modelers, not drone toy makers, crossed the size line. Now we have Model Aviation magazine celebrating the construction of models whose size and mass are in the man-carrying range. No, they don't have pilot seats, but some of the bigger RC monsters are heavier than ultra-light aircraft. The FAA has due cause to be concerned.