Yeah I'm gonna mention the changes I've done. But would they be considered aftermarket even though they are OEM GM products??
Any change on your vehicle from something that is not how it was originally purchased could be something they don't cover. I know with both of my last two providers, they make it very clear that any changes to the vehicle need to be documented (I'm sure that it is so they up your rates in the name of covering more stuff).
Either way, good thing no one was hurt.