A secure erase should wipe all blocks (and since it is done by the firmware, physical blocks, not logical ones), but there have been instances of buggy drives that don't actually do it properly.

Some SSDs also transparently encrypt all data written, and the key is replaced on a wipe command. Even if they don't wipe the data fully, it's now unusable, if the encryption works correctly.

Quite old SSDs might not support any of this.