Good, although I'd say "Hive" instead of "we" and mention the release number (with a link to this jira). Or should it be "the query optimizer" instead of "we"?
This can go in a version-info box at the end of the Join Syntax section, then a simple example can be added just for emphasis at the end of the Examples section. The syntax itself doesn't need any changes.
Your second sentence says that the column names can't be identical, so the first example in the wikidoc can't use unqualified column references: "SELECT a.* FROM a JOIN b ON (a.id = b.id)". But is it more restrictive than that – neither table can have an (unreferenced) column named the same as the other table's referenced column? Perhaps I'm overthinking this.
I can put this in the wiki after you fine-tune it, unless you'd rather do it yourself.