[LogicX]

My naive understanding is that SSDs have portions of memory that go bad. They then use other, reserved portions of memory. As a result, not all of the memory is exposed for access to the host OS, only the on-drive controller sees the full picture. As a result, you may (at this time) believe youve taken a certsin action, but the reality is that the controller has likely not done what you expect. This is how you may think you've erased everything, but in reality, have not.

[londons_explore]

The controller stops you accessing some parts of the drive, but it also stops the attacker from reading those same parts.

Only a very advanced attacker is likley to be able to read those reserved sectors and be able to reconstruct data from them.

I'd say you are safe from everyone except the drive manufacturer, state actors, and people with more than $50k to gain from extracting info.