Actual labeling laws won’t let you label a mostly plastic product “leather” the worst leather you’ll see called “genuine” (if they’re not breaking the law) will be something called a “finished split” which is basically painted suede.

Calling each type of leather a grade is actually the biggest myth in the industry. You can't contact a tannery to buy "genuine leather" as a specific thing.

All leather is Genuine, all leather that's not suede (bottom split) is top grain and top grain that hasn't been sanded (corrected) is full grain. The terms encompass one another.

The breakdown you sometimes see calling genuine, top grain and full grain grades is actually more like: "This is the worst you can expect with each of these terms in the description"...but unfortunately people have taken it as each term being a separate distinct type of leather which from an industry standpoint is simply not true; you can't call up a tannery and buy "genuine leather". So it's entirely possible for a company to say "genuine leather" in their brief description and then say top grain or full grain (and even more descriptors) when you click further (this was the case with an Article couch I bought).

There are also makers in other categories that use it just to separate it from synthetic Red Wing is a good example with an excellent reputation and they actually own a tannery: https://imgur.com/a/Tdtbjge

The “quick and dirty” full grain>top grain>genuine really only applies when you can’t find more info about the tannery or company making the item. There are top grain leathers and even suedes that come from top tier tanneries that I’d take any day over “full grain” cheap tanneries making leather for some of the big “fashion”brands.