Why are you inclined to believe this isn't the case? What possible reason would there be for Apple to care one whit about the email that goes to iCloud accounts? The only thing that makes any sense at all is virus/spam filtering.
No you didn't. They don't care what's on your phone. They care about two things:
1) What's on their store, and
2) How apps get on your phone, e.g. they must be codesigned by Apple.
The former is where they apply their content standards. The latter is a (very effective) security measure.
But, for example, Apple doesn't care in the slightest if I make a hardcore pornography app, sign it with my own developer cert, and install it on my phone. They only care if I try and submit it to their store. Similarly, they don't care if I open up Safari and visit some pornographic website, even if it uses HTML5 offline mode and gets added as an independent icon to my home screen.
You're acting like Apple has some vast conspiracy to eradicate objectionable material from the face of the planet. That's ridiculous.
Apple has been pretty open about the fact that they just care about what's on their storefront. The only reason that this effectively means they control what's on your phone is because most people can't install apps on their phone except via Apple's App Store. Although, as usual, everyone in the world is free to view whatever objectionable website they want.
The security implications of only allowing codesigned code to execute is completely divorced from the decision to control what content is allowed on Apple's storefront. The former limits what's on your phone, but does not make any judgement about the content. The latter makes a judgement about the content, but doesn't limit what you can run on your phone if you can find some other avenue to run stuff (e.g. self-signed with a dev cert, or web apps).