Apple M1 didn't come out of nowhere, they learned from everything that came before. Your comment sort of implies that the innovations came solely from being developed behind closed doors (or in some kind of vacuum), which denies credit to workers who made the thousands of incremental breakthroughs that landed in the commons and which has helped us to arrive in the place we are now.
No, GP made a pretty specific point: that vertical integration can clearly provide some serious benefits in the realm of computer hardware.
Now, the fact that vertical integration usually implies closed doors is relevant, yeah; but I don't think anyone is denying credit anywhere, and I think it's important to acknowledge upsides.
