Well … they did get it booting, so I’m not sure if “unbootable” is the right word either. But maybe I’m just mincing words. I’ve had a lot of devices that required some convincing to get it to boot again. But as long as it didn’t require an eeprom writer, I don’t call it “unbootable”.
I think Dlonk called it “nearly bricked”: Dual Boot Android from SD Card or Why It's Not Needed