While accepting the other replies, I do wonder how hardware trust is achieved. The security point about open source is peer review. For a dunce like me, I can pretty much rely on people much smarter than me to review open sourced code. In reasonable time, if there is a iffy routine buried in some bit of software, such people will out it. So, people like me can pretty much trust it, and even if something is missed but later found, again, we can be sure the discoverer will report it, while a commercial organisation might be motivated to hide it.
But, how does that work with hardware? How do we trust all the chips? How do we know there isn't something iffy built in at manufacture? Then, how can those same cleverer than me people discover it? How do they inspect the encased silicone circuit?
So, in that vein, I see the point you might have been making, and actually, I think its a worthwhile question. Because to me, it does look like what you describe, a sort of closed source hardware which runs all open source software. And I personally dont know that that is safe. Or is it?