@commonsaychel I know the guy who has the original letter. It says what it says. The main thrust to the relevance of this thread is that Rav Moshe ZT”L was uncomfortable paskening on brain death and so he openly and extensively relied on his son-in-law for the psak. Rav Tendler, Rav Dovid, and Rav Reuven compiled the teshuva and that’s how they wrote it.
So Da’as Torah isn’t infallible and often has to rely on da’as of something else.