Where do you read that it has 25% over-provisioning? I don't see that in its spec: http://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/ssd-dc-p3700-spec.pdf
The sentence "1 sector = 512 bytes or 520 bytes or 528 bytes" intrigued me tho.
The Intel® SSD DC P3700 and other Intel SSD's have oversubscription space, this is used by the controller for maintenance tasks such as TRIM and garbage collection. So, if your drive has 2 TB addressable by the user, you can be sure it actually has more flash memory built-in for overprovisioning.
At this time we are not able to confirm the information mentioned in the external websites, however, we will check about this and will provide additional information soon.
Note: The Variable Sector Size (512, 520, 528 bytes, etc.) is a feature of Data Center drives like the Intel® SSD DC P3700, it allows the user to format the SSD using a determined sector size to improve compatibility with some environments. This should not have any effect in the addressable capacity, VSS is available since some systems may work better with a specific sector size.