Hi 2sneaky,
It took a while to coordinate getting the Generic Shooter authorized to check out for testing nativisation. My results following your repro steps were (Following steps for Exclusive Nativization):
UATHelper: Packaging (Windows (64-bit)): UE4Editor-Cmd: [2017.03.07-19.55.54:467][ 0]LogInit:Display: LogBlueprintCodeGen:Error: BP /Game/GenericShooter/BlueprintLogic/BP_PlayerCharacter.BP_PlayerCharacter is selected for nativization, but BP interface class /Game/GenericShooter/BlueprintLogic/Interfaces/BPI_CanOverrideDamage.BPI_CanOverrideDamage_C is not
When I nativised that file, it would not successfully compile due to other erros so I attempted to repro the issue by nativising the ThirdPersonCharacter Blueprint from the Third Person Blueprint project template. (Note that the Generic Shooter is currently not tested/approved for UE4.15 so this may be the cause of the issue.)
This compiled successfully with the nativised asset, so the issue does not appear to be with a bug with nativisition per se, but something that needs to be adjusted in the Generic Shooter file to work with nativization.
If you can reproduce the issue with a project that is meant to work with UE4.15 specifically, we will continue to investigate the issue.
Thanks,
.