I purchased a 2020 Sierra AT4 with the 6.2 the fell in the date range of the valve spring issue, I have 6K miles, and I drive it hard, no issues with the entire truck, the valve spring didn't affect a large percentage of the 6.2s produced from June 1, 2020 thru Sep 15, 2020, valve spring were manufactured by an outside vendor, the problem was identified and corrected, so purchasing any 2021s or really late 2020s produced after Sep 15, the issue has been rectified, you'll be good, some people think its a widespread issue, but only affected a small portion of the 6.2 produced during that period.
BTW I LOVE that engine, its badass and get decent MPGs if driven lightly, Im averaging 15.9 after 6K, that lots of idling, off roading and city driving, the best 50 mile trip was 23.5, best 400 17.6, again that 400 includes a lot of the mentioned conditions.