While the local data can be deleted with "datastore format local", it is not securely erased. Unfortunately there is no capacity to sanitize Steelstore devices. To ensure data is no longer accessible at end of life, it is recommended to contract a drive destruction company who can provide chain of custody and certificates of destruction.
Additionally, we do not have a statement of volatility available for the Steelstore product line, so you would need to use your best judgement. Removing boot modules and RAM and then destroying those components is typically sufficient.