As Bigger Is Better says, Everything is better when it's BIG. This is just separating big-ness into its own distinct categories, aka a Tier System, instead of each individual size being a unique thing.

Usually used in Video Games, but can be used in Real Life for things like shipping costs, where a range of possible volumes all have the same shipping cost, so long as weight stays the same.

Smaller things are usually lesser in some quantity than bigger things, but they might just be a trade-off instead of strictly worse. Also, these tiers might be different in ways beyond just size, like color, or shape, as a way to show off visual variety instead of just being a scaled-up graphic.