OK
So no the bug didn't go away, it reappeared after restart. It's easy enough to circumvent with the factory test mode but annoying since it's the only tiny flaw. I'm going to try to re-flash firmware. Maybe something went wrong when I entered the wrong model number during the 3021 -> 3031A conversion.
Yes, everything is as you'd expect from the 3031A, 6A/60A ranges, 155 V-Limit, 70A C-Limit
I decided to be thorough and conducted a last test @60A. I scrounged up every last power supply and 5V power adapter and threw them in parallel. Managed to just scrape 60A @ 5V = 300W, though its pretty sketchy, had to actively cool my banana <-> spade converters.
Before I tested with the cover off, but this time taped my thermistor inside and ran the wires out of the cover, just to be extra thorough, so its completely nominal conditions. I ran the test for 60 minutes.
It rose to 63C pretty quickly, in around 15 minutes, and then stayed there. Well within the operating range of anything inside.
I'm going to call this good. Congrats to all 3021 owners, and my apologies for those who payed $1000 for the 3031.