Yeah, it was rubbing the Panhard bar. Interestingly, even when I put the old 265/70 in there it was incredibly close! It may be a manufacturing tolerance stack-up issue. I measured the distance from Panhard to the furthest point of tow hitch = 31". So there is definitely not room for a 265/75 on my 4runner.
Once I noticed this, I did a bit more searching and found that some people had the same issue, but others (like you) had zero issues.
Its all good though, the only time I have ever used my spare was in Big Bend, when I ignored the advice of a Park Ranger (back when I had road tires).