What do you mean by "displayed sideways"? I'm guessing you mean either:
1/ The toy inside the bubble is displayed at a diagonal angle, rather than perfectly horizontally or vertically.
2/ The packaging cannot be displayed on its side, front or back.

If so, to that I would say:
1/ Carded Universe figures are also packaged-displayed at a 45 degree angle.
2/ Henkei figures can be displayed on its side, front or back. Although I have no idea why anyone would want to display a carded figure like this.

...this sounds more like an issue of visual aesthetics rather than functionality though, unless I have interpreted your statement incorrectly.