In Griffith's Elementary Particles we are asked to draw all four vertex Feynman Diagrams for Compton Scattering. Most are straightforward but one puzzles me.
As has been said here: https://www.physicsforums.com/threads/special-fourth-order-feynman-diagram-compton-scattering-why-is-it-allowed.805039/
But my question is, does this not represent pair annihilation instead of Compton scattering? All other fourth-order Feyman Diagrams feature electron and photon going in and electron and photon going out. This one however an electron-positron pair going in and two photons going out. I understand that the two processes are related by crossing symmetry, but are they considered to be the same process or am i missing something important?