may be
This is called faith
In this case I decided trust the open-source community more than Apple, since the incentives of people inspecting open-source code probably align better with my own interests than the incentives of Apple.
The incentives of any people are: earn enough money for a peaceful existence.
When Heartbleed happened, it turned out that only a handful of people in the entire world have the expertise to do a full audit of the OpenSSL code. And their work is ridiculously expensive. And the audit didn't happen until someone paid for it [1] (I'm not entirely sure it ever completed [2]).
People may actually have less incentives to inspect open-source code because there's always the question of life, money, time, work-life balance etc. etc.
[1] https://www.zdnet.com/article/ncc-group-to-audit-openssl-for...
Regarding the Intel comparison, you have no choice but to trust them, but by using Apple products, you are trusting Intel and Apple, which is worse than just trusting Intel.