That's a bullshit video. The guy conducting the tests doesn't know enough about how SSDs work or about how Macs boot to be drawing conclusions, especially not such strongly negative conclusions. He would have had to at the very least attempt a tethered restore from DFU (as is done for these phone storage swaps or any other situation where the NAND is blank or thoroughly corrupted) before concluding that Apple has everything totally locked down.

Adding the second drive module is something that we should not expect to work the way he tested it. Plugging in a second hard drive to a desktop does not magically give you a RAID-0 without extra steps; expecting this from SSDs doesn't make any more sense. And without reverse engineering the machine config from the quoted prices, we don't even know if the two modules had the same capacity, let alone the same type and manufacturer of NAND (which is probably important if the system is going to treat the two modules as one SSD instead of exposing them to the OS as one drive).