Simply filling the disk by any means runs the risk of your incriminating (or whatever) information being retained in a sector that got remapped out from under you that you can no longer write to.

Wiping the encryption key takes care of that problem, as well as being much faster.

Thank you, this is what I was trying to avoid doing by simply filling an SSD with random data. As you mention, I suppose FDE is better, but now you have to ask yourself whether OS level or hardware level is best. In this case if you override an encrypted partition with a fresh OS installation it wont matter as much since most of what will be left will be gibberish.

Sometimes I do just that, I'll install Linux encrypted, and then reinstall later without migrating any bytes. My main concern is work related / personal finance documents being left over on a laptop. I've tested plenty of forensic utilities on my system after erasing files.