It might be designed that way to make the nutritional facts more appealing. They can define the portion sizes arbitrarily, so the per-portion amounts don’t look so high.

They can define the portion sizes arbitrarily, so the per-portion amounts don’t look so high

I dunno about y’all, but I cut my pizza’s into 1/8ths, which would be smaller than 1/5.

I’d be willing to bet that this particular pizza is very small, so most people would cut it into 1/4ths.