I can’t test it right now, but having done something like this a couple of years ago when the OEM SSD in my now-screen-dead rMBP semi-failed (and would go on to hard-fail a couple of months later before replacing it and, a month later, I ruined the screen), I tried a data retrieval using that adapter, to connect to my early 2011 MBP, via target disk mode. The adapter was on the rMBP side, obviously. Even though I have two of those adapters, there was no point to cap each end of the FW800 cable with one (though I suppose I could have, just to learn what might or might not happen).
As memory serves, this worked, but I would not be able to tell you which protocol icon appeared on the target mode screen saver.