“Rounded corners” is literally all there was to Apple’s design patent. They drew a drawing of an iPhone, made up of solid and dashed lines, then put a note at the bottom saying “only the solid lines form this patent”. The solid lines were a 2D image of the rounded rectangle of the outline of an iPhone along with the rectangle of the display itself. That was clearly a frivilous patent. This is not so clear, and I think meets the bar of a novel implementation. You keep saying it doesn’t, but you haven’t given any solid reasons why.

The "rounded corners" falls into a different category of patents known as "design patents" which seek to protect a non-functional design of something. The ones that we tend to be more familiar with are "utility patents".

Also in this category of patents, Coca-cola's bottle (from 1923) https://patents.google.com/patent/USD63657S/en (this is a more updated version than the one that was in the Wiki article which is the original one).

https://en.wikipedia.org/wiki/Design_patent

In the United States, a design patent is a form of legal protection granted to the ornamental design of an article of manufacture. Design patents are a type of industrial design right. Ornamental designs of jewelry, furniture, beverage containers (Fig. 1) and computer icons are examples of objects that are covered by design patents.

https://www.uspto.gov/patents/basics/apply/design-patent

The elements of a design patent application should include the following:

1. Preamble, stating name of the applicant, title of the design, and a brief description of the nature and intended use of the article in which the design is embodied;
2. Cross-reference to related applications (unless included in the application data sheet).
3. Statement regarding federally sponsored research or development.
4. Description of the figure(s) of the drawing;
5. Feature description;
6. A single claim;
7. Drawings or photographs;
8. Executed oath or declaration.

All that is needed for Apple's "rounded corners" design patent is indeed just a drawing.

From the standpoint of a design patent, the rounded rectangles is not a frivolous patent.