No, they're a tad wider, I had the 33x12.5/15's and the 305/70/16's side by side...the 305's are wider than the 12.5's....I measured the tread width (Not to be confused with the section width.

The 70 series aspect ratio is less of a balloon in profile than the 75 series aspect ratio...and you get more tread width for your section width...



(Note the non-balloony appearance)

So my 305/70/16's have a tad wider tread than 33x12.5/15's...and are a tad taller as well...and are less balloony too.