Feels like killing a feature for the sake of an edge-case. What's the prevalence of malignant entities taking over a Facebook account (of all accounts you can nick) via PGP takeover?
Facebook account takeovers are really elaborate and very common. Since this is a very easy way to essentially block users from recovering their own account, I can see why they're killing this vector. The account was not taken over through the feature, but the feature made self-service recovery near impossible.