I have not looked at BPC but I have an idea what’s going on: Many “paywalls” operate by letting you download the full content of an article but covering it up with an overlay imposed via JavaScript code.
You’d be surprised how many so-called paywalls stop working when you turn off JavaScript. Presumably at least part of how BPC works is simply blocking the JavaScript from covering up the content already transmitted to you.
So this is what passes for circumvention these days: A publisher sends you the full content of an article in a web page, but you decline to run hostile code that would like to hide most of the content you have already downloaded.
We are a long, long way from DeCSS. At least that involved decryption. This essentially criminalizes “view source.”