Have you had a case where the SSD is soldered to the logic board, and so exposed more directly to whatever might damage the board?
Apple has reportedly claimed data can be recovered from the SSD if the logic board fails but the SSD doesn't. The link given above leads to this explanation:
https://9to5mac.com/2016/11/24/apple-special-cdm-tool-macbook-pro-ssd-recover-repairs/
As I said previously, the logic board must be able to enter target disk mode for that tool to work.
If the logic board is completely dead, you are SOL.