I don't believe that AWS sells its retired equipment, at least I could find no evidence for it and thus I think the likelyhood that someone gets a hold of an unwiped/unshredded SSD from them to be exceedingly low.

I am surprised that drive manufacturers haven't built in encryption at rest though since it would be pretty easy to generate a key on first boot and then make it easy to wipe by just making a new key and thus essentially scrambling all the data on the disk instantly without having to wipe them at all.