Ya, constraints doesn't mean they are unavailable it means limited supply and are handed out to dealers in a way only GM understands. Right now 1LT is constrained this month. Weird as it's a lack of extras. <shrug>
Funny. I didn't get Z51 because I didn't want a wing! lol (no wing delete in 2020)
Z51 is constrained so it might not have been available to you anyway.