Final answer:
Django Reinhardt, a Belgian jazz guitarist, incorrectly believed to have used only two fingers and the thumb of his left hand, actually had limited but not exclusive use of his other fingers.
Step-by-step explanation:
The assertion that is false of Django Reinhardt is that he only used two fingers and the thumb of his left hand. Django Reinhardt was indeed a pioneering jazz guitarist who played a significant role in the development of gypsy jazz. However, while it is true that he was limited in the use of his left hand due to injuries from a fire, using mainly his index and middle fingers for soloing, it's incorrect to say he only used two fingers and the thumb. He was able to use other fingers, albeit with less dexterity. Moreover, Reinhardt was indeed of Belgian nationality and not, for example, French as often misconceived.