The trust usually comes because the small company assumes the big one wants to make money by completing an actual product line and selling it - normally the way just about everybody thinks Capitalism works. The small company says to itself, well, they've got to have X (like Sapphire coatings for screens) to make money - they can't actively want us to fail and take steps to make us fail or they take a hit too. So what we have to do is deliver the component at the price where they still make money, and as long as we do that, we're on the same side. So the small company focuses on distrusting the contract clauses it thinks are rational to distrust, in ways that it thinks might allow abuses a rational but dishonest actor might try..
It's like buying a car and thinking you can't trust the salesman to tell you the truth - only you should have somehow known the salseman wasn't the real salesman but a psycho-killer who had just slain the real salesman and the big thing he wanted wasn't to make too much money selling that car, it was your home address so he could pop by at 2 AM with his skinning knife collection. Most people don't go through life checking with NASA in case the persons they are dealing with are secretly space ailens.
From the summary, Apple seems to have had control over the decision to install back up power supplies, and to have chosen to save money on them instead. That sounds like an Apple executive brought in a good quarterly bottom line and then got out before the product couldn't be made as specced, and to heck with whether Apple still looks good five years down the road. The big company takes a small hit, the little one goes bankrupt. Apple is by this definition exceptionally untrustworthy, just because they won't take as much damage as their smaller subcontractors, or individuals, but if that's true, then Capitalism is a system where the bigger a company gets, the less it should be trusted, just for sheer size, and smaller businesses and customers should rationally start distrusting sheer bigness. How about that, free-market types and Randroids, do we need stronger Anti-Trust laws? The other solution seems to be extreme paranoia. If great market share or rapid growth mean everyone should regard that company as exceptionally untrustworthy, they why doesn't it make sense for consumers to always pick a smaller competitor for everything?