Seriously, dude? I understood it was an editing error, and said I meant before R&G came out. And you feel the need to correct me, assuming I misunderstood something?
And that was the answer. The reason it's in the core book is because it's an
error. That was true immediately upon the core book's release. There's no "before and after" here - but incidentally, the knowledge referenced
long predates R&G.
Hell, look at the post date for a second - back in January, versus R&G going live in April. The quoted post is
the entire answer to your question. If there was some kind of "before and after" thing in play here, that post's timing would land it firmly on the "before" side.