You can apparently do that with Galera, but I haven't seen that in production.

What they're referring to is most likely MySQL's half-baked "circular replication". Some people claim it works for them. Personally I tried it once and the usual MySQL replication issues (desync, InnoDB deadlock) would create much more uncomfortable situations than in a Master/Slave setup.

With master/slave you at least stand a chance of having one half of the pair survive through a problem. With circular replication the cluster would lock up hard almost every time for us, and - to add insult to injury - leave the pair inconsistent after recovery.