I don’t think Apple is going to dump a 15 year relationship with Intel over iGPU specs.And because Apple is good at negotiating and AMD is competitive for the end customer, I'm pretty sure Apple could also get excellent pricing from AMD - with the added bonus that the integrated GPU would be leaps and bounds better than what Intel has to offer.
Also - in order to keep up the negotiation pressure, you need to demonstrate that the competing supply chain is for real and not only on paper. Intel sales guys are not stupid.
And regarding negotiation pressure, what’s your point? That Intel won’t be willing to sell at a price acceptable to Apple until after they get dumped?