Sadly you are in a bit of a pickle! Apple uses RAW flash modules not true SSD's which can confuse people. A true SSD has a controller and RAM besides the Flash storage modules.
For reference here's what a iMac Pro or the current MacPro uses
[image|2619803]
The Red marked chips are the Flash and that little tiny Orange chip is the ID and buffer chip no Controller or RAM!
Now lets look at a Samsung (Apple custom) blade SSD
[image|2619807]
Here the Red Marked chips are the Flash and the Blue marked chip is the Controller and also has the RAM within it.
Unlike the Samsung SSD the iMac Pro uses the T2 chip as its controller! And as you also guessed the T2 if left on default will encrypt the data held within the Flash chips.
So sadly you can't remove the Flash units and install them into a different system (another iMac Pro or anything else). You'll need to visit an Apple Store who has in-store staff who know how to service your iMac Pro if you really need to retrieve your data. There is a small (and I do mean very small) possibility they can gain access to the data if you had altered the setting so the drive is not encrypted.
Otherwise unless you don't backup religiously and/or work off of an external dual sync drive your toast!