Admittedly, paywall-busting doesn't work as well with Unclutter as with the text-extraction methods. But it's still effective for most sites and there are custom tweaks e.g. for nytimes.com.
I'm thinking about improving on this actually. It would be cool to fetch the page content from web archives automatically if it detects a paywall. Kind of like the "archive.is" links people post here all the time, but with less clutter.
Is that paywall busting even an actual goal/requirement in reader mode, or just a fortuitous side effect of the way it does its "web clipping" (is that still a term?)
It's an intended side effect. The paywall banners are also just clutter to remove from the DOM, often the entire text is still there.
Technically, messing with paywalls is forbidden for Chrome extensions listed in the webstore (and detrimental for getting press coverage). Which is why no one advertises this.
Quite often, you can get through many a paywall by switching to reader mode and then reloading the page. Previously hidden content appears.