I would assume that Apple looked into it a little bit. US companies can get in trouble if their contractors abroad use slave labor, buy parts from the wrong country, or divert part of the contract to use as bribes. So I doubt this is a case where everyone at Apple laughed about how it was too good to be true, CC'd the lawyers, and the lawyers wrote back "yeah hahah".

At the end of the day, you can't always find everything even if you try really hard.

You can make it yourself if it is important enough.

Why would it be too good to be true? They might have simply won the deal but a small margin against a competitor.

They also might have hidden this info, or even fraudes their way through.