Hmm, looking at the code I'm not sure how that could happen. Did you perhaps load into the afterword from an old save? That would do it as everything automatically unlocks on that page.
And thank you - I'm glad you liked the new content!
That's...entirely possible, actually. On loading my previous save, I may have advanced to the post-game screen before scrolling back to a point where the new chapter could start. I didn't realize that would reveal the bios in their entirety. Thankfully I only saw the one, minor spoiler. I'll be careful to avoid that in the future. I appreciate the insight.