It's not a perfect ellipse, why?

I'm pretty sure this has been done before but never understood why. I was just studying Hoefler engraved text and noticed the O wasn't a perfect ellipse as marked in the image below. The overlay on top in yellow is the ellipse and the bottom in brown is from hoefler text. Is there a reason why they do this? If you look at the gif  as seen here, assuming its to make up for width optically and even if I pulled the side anchors it looks off in the corners. Not to mention the anchors on the side are not center aligned for the O in hoefler's version, its like it's been pushed up a little. The green stroke aligns with the anchors from the brown text and the orange stroke aligns with the anchors on the yellow ellipse. Maybe I've over analyzing this but I'm kinda curious why its off centered and it's not an ellipse.

Thanks.
Edited image cause the first one was the wrong image.



Thanks