Being a Jounin doesn't mean you can open the gates. You have to know how. I mean, if what you're saying is true, Kakashi should be able to use Rasengan just because he's a Jounin, yet we've never seen him use it. According to Kakashi, only Jiraiya, the 4th, and Naruto can do it. currently, Lee and Gai are the only ones we've ever seen open the gates (if you don't count Kakashi as opening one when climbing the rocks).