Service Center Drive Erase is capable of two different types of drive erasure; firmware based erasure and block erasure.
The reason that block erasure requires substantially more time to perform a drive erase on a device is because it writes values across the entirety of the device a block at a time. Whereas firmware erasure, or otherwise known as Cryptographic Erasure, is performed by sanitizing the cryptographic keys used to encrypt the data, as opposed to sanitizing the storage locations on media containing the encrypted data itself. By deleting the cryptographic keys used to decrypt the data on the disk it renders the data irretrievable.
This process of media sanitation is a NIST compliant standard for data destruction. If you would like more information on NIST media sanitation guidelines, you can find it at the link provided below.