There's more detailed information on a different page[2] including the following quote which I think supports the general rule I listed in my original comment:

> ...[Amway's] sales plan was not an illegal pyramid scheme. Amway differed in several ways from pyramid schemes that the Commission had challenged. It did not charge an up-front "head hunting" or large investment fee from new recruits, nor did it promote "inventory loading" by requiring distributors to buy large volumes of nonreturnable inventory. Instead, Amway only required distributors to buy a relatively inexpensive sales kit. Moreover, Amway had three different policies to encourage distributors to actually sell the company's soaps, cleaners, and household products to real end users. First, Amway required distributors to buy back any unused and marketable products from their recruits upon request. Second, Amway required each distributor to sell at wholesale or retail at least 70 percent of its purchased inventory each month -- a policy known as the 70% rule. Finally, Amway required each sponsoring distributor to make at least one retail sale to each of 10 different customers each month, known as the 10 customer rule.

Lastly, just because people disagree about the nuances of the rule, does not mean the rule doesn't exist. I feel very comfortable with my original statement, and those in favor of e.g. Herbalife would vigorously argue that meet my definition of MLM, while those who think its a scam would argue that they don't meet it.

1: https://www.consumer.ftc.gov/articles/multi-level-marketing-...

2: https://www.ftc.gov/public-statements/1998/05/pyramid-scheme...