Unfortunately, FPCM failure seems to be relatively common. As mentioned, mine went out at 320 miles, I hadn't even owned the vehicle for a week at the time, so it was new-new. Must have been a defective part from the supplier to go out that early. That was in September, I got it back a day or so later and now have 2,500 miles with no further issues as of yet.
I saw your other reply about the dealership finding metal in your oil, so it seems you might have a more serious issue. Metal in the oil basically always results in needing a new engine. Please keep us updated, it's good to share the experiences we have with these vehicles. I feel for you though, having a new vehicle engine brick itself is an awful experience, it's highly inconvenient, and erodes trust in the vehicle even after repair. Being it's so new, warranty should handle the repair and you'll get it back in working order, but it still takes a toll on time, convenience, and trust.
Regarding your question about 5.3L failures under a year, besides a period of time around 2021 when GM received a bad supply of lifters, having a 5.3L fail within the first year is unusual. I'm on my third Tahoe, and my prior two both had the 5.3L. My 2008 went 11 years and 160K trouble-free miles, my 2019 went 5 years and was at 50K trouble-free miles when I traded it in, it was running perfect at trade-in, I just wanted a new gen with the 6.2L. My experience with those two 5.3L engines was excellent, they never let me down and a reason I'm a fan of these vehicles. I'm hoping my current 6.2L will serve me reliably, besides that little hiccup at 320 miles with the FPCM.