Yeah, the steer is also dead, stuffed, and mounted on that wheeled platform in this picture. The article talks about that. I think Popkin just assumed the picture was from when he was still alive.
I suspect the 6.5’ was measured when he was still alive and had his head lifted up higher, and I suspect his length was measured with his tail extended. This size could still be exaggerated a little, but it’s probably not way off.