If you use on-board crypto on most SSDs, there's a dedicated place for key storage and using the SSD's onboard wipe feature just changes the key and TRIMs the whole drive.

Most of these drives use cryptographic keys even if you don't use a password on the device. Think about it as an SSD manufacturer - what's the easiest way to wipe a drive? To actually go and zero out every cell on the disk or to overwrite a very small cryptographic key with a new one - effectively destroying the data without the need for any other write cycles to occur.

Pretty easy to verify - if you have an SSD with support for this, which most do now.