A lot of privacy fanatics (myself included) are also open source fanatics. I like to be able to wrap my own tinfoil hat even if it is harder and a bit more uncomfortable.
> Does this mean that open source is more important than privacy to people of this mindset?
Not exactly, but I think the questions should really be something like "who is the guarantor of your privacy?"
If you are happy with it being a corporation like apple then you're fine. I'm not, and what we consider more secure would have to be a much deeper conversation in which we actually define our threat models.
Besides that there is also all of the transitive points, like what does apple trust? What does google trust?
I'm not sure if I'm more secure, but I am sure that I have less people influencing my security and that I have a reasonable way to validate them.