Itll just destroy one of your rear window segments. Some trim will melt also
F150s have had this problem longer than chevys from what I've gathered and they've issued no recall so +1 for gm. I e looked on some f150 forums and it seems to ne that debris caught in the sliding window or something else bends one of the contact tabs basically arcing across the larger gap and causing big time heat resulting in melted window trim and eventual glass smashery.That's my current conclusion which is subject to change.
I was called to bring in my 2018 Lt so they could pull the defrost fuse. If I can adequately see the contacts and periodically inspect them I might just put the fuse back in as I use my rear defroster dammit! We have cold temps up here.