This happens on mine too. I took the insert out so that my iphone 7plus would fit.I recently observed quite a noticeable flow of very cold air coming out of the cell phone charging "pocket" (as the manual calls it). I can see the logic of having a wee bit of cooling air coming through there so as to keep a charging phone from overheating but the amount that I'm observing is really excessive, at least at ambient temps of below freezing. I haven't thought to note whether it occurs on my Bolt only at speed or anytime. The manual makes no mention of any intentional cooling aspect.
Is this just some sort of a defect with my car or have others noticed the same?
Early on I 3D printed a base that fits in the slot to make a dock for my phone. Now that it is cold out, I feel cold air coming in. I believe the worst culprit is the little punch holes on the passenger side of the slot. I plan to put a piece of electrical tape over them and have designed (yet to print) a new cap for the slot, to close it in significantly and reduce airflow through the pocket.