The term "Generative" in "Generative art" has a pretty well-defined meaning.

Your comment is like saying that you don't think PHP arrays should be called "arrays" because element indices aren't necessarily strictly increasing. You can think that, and there's some sense to it, but it's still called "array". Similarly, you can't change the meaning of a commonly accepted term just because someone buys something at Amazon.

Assuming the OP's project can be called art, it's definitely generative. The artist does not choose which item is purchased.