In theory yes, but I'd wager that most of the time logouts are just hyperlink (/account/signout, /logout, etc.). Unless you had a good reason to, you kinda have to go out of your way to make it a POST.
What's your point? Google must be incapable of poor design? Everything a big company does is good?
Also, full disclosure: I work for Google.
<iframe src="https://accounts.google.com/Logout" width="0" height="0" ></iframe>"X-Frame-Options" is used to defend against click-jacking attacks, not to defend against CSRF.
<form id="form" method="post" action="https://accounts.google.com/Logout"></form>
<script>$('#form').submit()</script>
This is the very essence of the problem.
Someone sends you a link, you click it, it loads in your web browser telling you that you've sent them $5000. That is why POST, PUT, OPTIONS, and all the other methods exist.
This is most certainly poorly designed. Just because most web apps and web app developers suck doesn't mean that the freaking HTTP Standard should be changed.
Just no... please stop.