The related commits are years old. This isn't new. Last commit to that line was 3 years ago with the comment "unblocking embedding of twitter timelines".
https://github.com/brave/browser-laptop/commit/c4cd7c1dc41a0...
Also I just realized that is an archived repo that isn't used any more.
I took a quick look through the newer repos and couldn't find any kind of hard coded whitelist like that.
Am I missing something?