2020 Denali HD here, Bought in October of '19.
Didn't see a leak for the whole first year, I typically parked flat, or with the nose going uphill.
For a few weeks I had my trailer attached to the truck and had the truck facing downhill and didn't drive it...when I finally got back in and loaded the cab up, I noticed all the under-seat storage was wet.
I happened to get a phone call from my salesman for the 1yr anniversary the day or two later and I mentioned the problem. He said it wasn't officially recalled, and customers weren't notified, but they knew about the leaks on the trucks and GM covered it when the customers brought them in for service. I brought it in about a week later to get it resealed and haven't noticed the issue in the past 3 months.