Private label / contract manufacturing
A manufacturing model where a contract manufacturer produces a stock formula and sells the same batch, unbranded, to any brand that wants to put its own label on it ("private label" or "OEM" manufacturing). It's a normal, legal, and common way simple, commodity formulas reach the market -- it's why the exact same formula so often appears under many different brand names.
Example
213 products, sold under 92 different brand names, share the exact same "Super CoQ-10 100mg" formula -- one of 3,699 such exact-formula clusters covering 15.3% of the on-market catalog.