(2016), this is still technically true, but "utf8mb4" is the default encoding since MySQL 8.0, and "utf8" is a deprecated alias for "utf8mb3", so this isn't nearly as much of a footgun.
Realistically, the alias for "utf8" should have been changed at a prior major version change. In that it would pretty much should only affect new DBs and even then would make far more sense.