You'll face the same issue again if you reboot your machine (and most likely if it goes to sleep and wakes up again). If you leave your machine alone (not running any tests) for another 10-15 mins and run the test again you may see improvement and speeds of ~ 250-350 MB/sec. Running any speed test (Black Magic or AJA) with that disk as a target on Monterey you'll initially see speeds of approx 1-5 MB/sec. Accessing files via Finder is like slow motion animation as you click on a directory and it expands to show contents, etc.

Eventually it'll mount (~ 5 - 10 mins) but once mounted will be slow. When you hook up this small drive (500gb) - encrypted APFS - it takes way too long to attempt to mount. On Monterey (M1 MacBook 14) its dog slow / almost inoperable. The device takes FOREVER to get recognized by Monterey. I've a 500 GB Sandisk Extreme (v1) USB C. Whether it's Monterey (Apple) or Sandisk - the issue is significant. As even after it may actually finish there is an issue that is happening and it will happen each time your machine reboots (and probably wakes up from sleep also). Waiting for many minutes to hours on end for a erase / format operation isn't really the solution.

Disk formatting never ends