If you're dealing with Apple/an Authorized Service Provider, there is a replacement method available to them to get data off of a failing system. (Uses the USB-C ports and DFU mode).
Anecdotally, it does work on some boards that are otherwise hosed, but may be less frequently successful than with the prior data connector, as there's more pieces that do have to be still functional for it to work.
Interesting to note that the T2 chip in the new MBP supposedly contains the HD/Flash controller that used to be a separate IC -- according to the specs page. As it's a pretty fully featured SOC in its own right, that might make it easier to get to the HD in case of main CPU/RAM failures.
