I have heard it from somebody - not a rabbi - that explained it beautifully, but as literal .
I would bet that he heard it from a rabbi. Whose rabbi was considered by many to be some "authority".
Misnagdim don't talk kabbalah from every website. So you may not hear the literal reading much.
Whereas Lubavitch, maybe Breslov, and maybe all Chassidic groups, are more open to teaching kabbalah. And lubavitch are on the web.
The guy that explained it, said that Rabbi Aryeh Kaplan's book "inner space" explains it..
Perhaps that explains it literally.
The vilna gaon wrote about it literally. If you want authority, that is a huge authority. Just not your authority. And even if you are right about this 1 student, people don't dismiss him because of 1 student, o. The VG said what he said.. There are these 2 positions.. And at the time, I think the vilna gaon actually wrote his kabbalistic thing to challenge the chassidic version. So the VG would have been aware of the non-literal interpretation during his time. And was most likely responding to it.
The fact is.. The issue was never about tzimtzum. It was about the chabad kabbalistic idea of G-d clothed in a body(which you say is metaphorical, like the statement in the tenach that we are made in the image of G-d). Some people - rightly or wrongly - don't want it discussed here, because they say it is heresy(as do most orthodox jews, including most chassidim and many/most in chabad). There are alot of people who are ignoramouses of judaism, who don't know a chassid from a misnaged, a neturei karta from a satmar.. And they certainly don't know about this chabad controversy, and that you are on the conversial end. And So it some decided, perhaps rightly - that it would be better not to discuss this rebbe G-d thing here.
That is really the issue.
Nobody need to be rejecting a particular understanding of tzimtzum between the Vilna Gaon, and (authors of) The Tanya.