If I had to guess what happened, some intel people pushed this as a feature, probably pushing it via one of the x86 git trees, and Linus either (a) didn't notice, or (b) didn't understand the implications, and then Matt quit in a huff --- by just stopping to do work, and not even updating the entry in the MAINTAINERS file. (That didn't happen until I took over the random driver again.)
It doesn't really look like he had NAKed it on paranoia grounds, but more on design grounds; others brought up the paranoia arguments. You were even involved in that thread, so you should have seen his stepping down, although he didn't submit a patch to MAINTAINERS.
Regardless, I'm glad that paranoia did eventually prevail, despite Linus's original strong objections.