[elaineo]

Google doesn't demand anything. If your paywalled website is not accessible by Google's crawler, then Google will not index it. Publishers want Google to index their pages and drive potential paying visitors, which is why they open the loophole themselves.

For the second point, Google does require that publishers specify "registration required" in their sitemap.

[GigabyteCoin]

If you're showing Googlebot one thing, and visitors who visit your website through google another, that's essentially "cloaking" (a blackhat SEO technique). At least it used to be.