the “official matrix website” is basically a wiki that people happen to have PR’d against; it’s
updated best effort.
In practice EX has threads, 1:1 calls, spaces and SSO now (threads and spaces in labs, as per the OP, but usable)
At least a while ago Element X broke bridging in a pretty annoying way, since all chats with more than 2 members were classified as groups, even if they were marked as DMs.