No, factory reset is the only form of data erasure supported on Meraki products. Ensure you hold for ~15-30 seconds.
You can verify the unit has reset back to factory settings (and therefore has erased customer content) by powering on the unit without an internet connection (else it'll just download the configuration again unless you've removed it from the Dashboard network/org) and:
MX & MS - access the local status page of the unit and you'll see the network name is not set
MR - will likely broadcast "meraki-scanning", "meraki-setup" or "meraki" SSIDs