Big Sur 11.3 appears to have corrupted my 4TB G-drive:
I doubt that this originates from software. The Knowledgebase article Apple Computers and Displays: Powering peripherals through USB contains some general guidelines and illustrates using System Profiler to provide information about the output (according to specifications) of a Macs USB ports...
forums.macrumors.com
I learned a big lesson. I am going to get the drive replaced under warranty, but will get a separate external drive just for my M1, because it looks like there are some serious issue with Big Sur and M1 Macs where it likes to corrupt external devices.