Apple is using a custom connector for the SSD in the new Mac Pro

Malcolm Owen for AppleInsider:

The new Mac Pro is a highly modular computer, making it ripe for upgrades and on-site servicing. But, the connector used for the built-in storage suggests replacements may have to be bought from Apple directly.
The flash storage modules will be offered in four different setups: One 256GB module, two 512GB modules for 1TB of total capacity, two 1TB modules for 2TB of capacity, and two 2TB modules for 4TB of capacity. Storage is encrypted by the T2 Security Chip, similar to other Mac models.
The information Apple provides isn’t enough detail to confirm what kind of SSDs are being used by the Mac Pro, but what the image reveals is that it isn’t any standard SSD that is in use with other devices… It also doesn’t appear to be the same sort of connection Apple uses in some of its other products, as far as AppleInsider is aware.

MacDailyNews Take: Sounds like this is a security (T2) issue, but we’ll wait to see what the deal is when Apple ships Mac Pro units to customers.