Had a chance to contemplate this more yesterday; had lunch in a cafe in a nearby town that displays work by local artists. The current work was photography by a woman with impressive credentials (Antonelli School and LRPS) and included some film stuff even! What caught my eye were some pieces with square prints, maybe 8x8 inches, in a 16x20 frame, mounted with top and sides equal. That's about 4" top and sides and 8" at the bottom -- really looked strange. I definitely prefer the optical centering.
As many threads do, this one has wandered a lot. It was started about the framing, not the printing, but hey, it's all good clean fun.
Just another data point ...