I worked in, and around OEM electronics since 2007.
I've seen many guys like Tim Cook, most worse off ones.
He squeezes suppliers, and know what he is doing.
Others squeeze suppliers, and don't know what they are doing.
On one of my first jobs, I've been witness to one such negotiations down to single cents, and microns of plastic for a few million units customized charger order.
The order was such a whopper for a small sourcing agency, that higher ups were willing to do just anything to not to spook the client.
Our guys quickly understood that the consultant guy doing negotiations on behalf of the client was a round idiot with a level of engineering knowledge of a first year dropout.
He kept insisting on completely bizarre design changes, and ridiculous cost cutting on design like using 2 cheaper through hole diodes in parallel instead of one a cent more expensive (did not believe my ears, the guy failed EE101 right here,) dispensing with NTC inrush limiters, removing safety caps (he did not know what they are for) and asked us to redo the mold 6! times in order to save some grams of plastic per run.
We managed to at least push back on safety critical parts, on a point that it will fail the certification.
Many years later I found out that the design of the first Kindle charger exactly matched the one we did in everything, but having an extra label.
And 5 years ago I learned that Kindles had multiple issues with melting chargers, and safety recalls.
9 out of 10 companies in the supply chain will just shoot themselves in the foot if they go on doing it like that.
Nobody will point how unreasonable your demands are if you are a giant multinational corporation, moreover so in China. If you do this, and don't know yourself if you are asking a for something stupid, who will know? No one will.