They also need high volume guaranteed before they can put any part in an iPhone and they probably want it to be tested enough to not explode in the user pocket.

They also need high volume guaranteed before they can put any part in an iPhone and they probably want it to be tested enough to not explode in the user pocket. It's challenging to achieve for a new part. It's like there is money for much better and much more expensive... but it doesn't come for free.