There will be a lot of opinions on this one...

I think the main driver to Pattern design is "function, within the ruled parameters". Without trying to discuss the evolution of Pattern design in detail, (which I'm not an expert on, anyway) I'd say that each year's list of maneuvers has always forced certain design criteria, and that most (but not all) designers try to nearly fill the "allowable size" box, to decrease wing loading. But...

It's not all about span, as far as wing loading goes. Decreasing the aspect ratio can easily force more area into a shorter span. There's also a trend toward thinner airfoils than in the past. (approximately 10% thick, versus approximately 15% thick, several years ago) Designers will use traits that are "good" to them, although another guy with different habits and experiences may disagree. ALL aircraft designs are some sort of compromise, as you know.

Still, if you compare 100 Pattern planes today, (which I did, with a friend's help, a couple of years ago) you'll find the proportions very uniform for all but a very small percentage.