No, of course not. I also can't build an iPhone from scratch or look at the hardware design or firmware. It's especially bad when you consider that Qualcomm baseband and the problems it has.

Hell, I can't even trust that with my desktop computer. Further, how do I know the light in front of me isn't fabricated and that I'm not a brain floating in fluids connected to a simulation?

Realistically, I believe Apple's intentions are in the right place. And I believe that, for the most part, iPhone backdoors are not a thing yet. Being able to look at the client code is not something I believe will happen, but I believe it would be good if it did because then the security of iMessage could be independently verified much easier. It is true that Apple could just lie about it and put different code up, but assuming their intentions are in the right place, it seems like a win-win for everyone.