You're missing the point. Google and Apple are trusted sources in the real world. In the real world, people say things like "I have an Android" and advertisements say "Get a free Android with contract" If the distinction there is lost, I don't think you can expect the general consumer to know that Google isn't a "trusted source" by the definition of FSF advocates, right? Nor, I would contest, that they need to.
>Hardly, if this kind of thing is allowed in their marketplace.
They'll move on this just like they started actively patrolling the Play Store for malware. Because they are a trusted source, even if they aren't an FSF definition of trusted source.
Obligatory response that you're not relying solely on your own ability to examine code for problems, but the entire universe of those able to do so.
With proprietary code, you're restricted to audits done by those whom the code author has allowed to do so (or who have surreptitiously obtained the source ... and having done so, put themselves at legal risk by disclosing their findings).