The video demonstrates the 1:1 coin size case and speaks about the curvature of the line it rolls on, but your thought experiment makes it a lot clearer. As th

The video demonstrates the 1:1 coin size case and speaks about the curvature of the line it rolls on, but your thought experiment makes it a lot clearer. As the size of the other coin goes to 0, the amount "gnawed off" of the rolling coin will also go to 0 while obviously still rotating a full revolution.