Why does "simulate Physics" on sphere collision prevent "OnProjectileBounce" From Firing

Basically I am working through the networking tutorials, my “OnprojectileBounce” event was not firing because simulate physics was activated on the sphere collisions setting in the viewport. Why would this stop the event from firing even though the sphere was still bouncing? I turned it off and it works but when its on it doesnt and I dont understand why

Here is the tutorial: