You declare the markets. The languages follow from that.
A passport is not translated once and then forgotten. You state which markets the product is placed on, and the page answers each visitor in the language of their market.


A market is a fact, a language is a consequence
Placing a product in a country is a commercial decision you have already taken. Which languages are needed follows from it, without you keeping a separate list.
Only one of the two negotiates language
The product address answers in the reader's language. The address of one published version is a fixed object, and stays in the language it was published in.
A visitor from a market you did not declare
They see the page, in one of the languages you declared. They are not shown a machine translation, because a translation you have not approved is not product data.