Are waves reflected off a transmission line when they reach the generator dissipate there?
Let us look at life from the perspective of the traveling wave front. It enters the transmission line, which has an impedance of 50 Ohms, and it is happy. There is no reflection because source and line are matched. V/I = 50. The wavefront travels in the transmission line and is happy in its V/I = 50 world. Then wavefront reaches the 200 Ohm load, and now it has a problem. V/I = 200. The energy that has traveled down the line cannot be delivered to the 200 Ohm load without changing V/I. SO, at that point, a reflection is generated that travels back toward the source. That reflection is a traveling wave in its own right, and behaves just the same way as if it was generated at the load.
The reflection travels back toward the source, and it is happy in its V/I = 50 world. Then it gets to the source, and the 50 Ohm resistor of the source allows it to deliver all of the wave energy to the resistor while still respecting V/I = 50.