FANG also has many lines of business where each one would be equivalent to a startup sized company. You can have way more impact than you think, on the specific product you work on. You'd be surprised how small many engineering teams are at apple for example, working on discrete products used by hundreds of millions of people.
My understanding is that he was referring to impact on the company. At FANG, there is no single product where your impact has a significant impact on the company as a whole.
Sure you can go to AWS and work on Lambda. And then you can work on a feature of Lambda. It's very likely that the feature is going to have an extremely minimal impact on Amazon as a whole company.
I'd imagine the same is for apple. You can join, go work on a secret feature of a feature on the iPhone, launch it, and then yay. You've now contributed to a feature of a feature of a product with 100s or 1000s of other features.
