This looks like it might be it:
The drive doesn’t provide 4TB of storage either, considering the single NAND chip. That means if you were to attempt to write that much data to the SSD, at some point it would either fail or start overwriting existing data.
I hope I’m wrong! I’d definitely consider buying some — hopefully you can report back with results. If they’re slower than advertised but have the actual capacity that’d still be awesome!