Was trying to reply to an article earlier. I had the same problem with being told I needed to solve it CAPTIA but there wasn’t one on the page. I assumed it was an error of accessibility with using high contrast mode and a screen reader, but apparently not.
Using iPhone on iOS 11.4 I think. Also accessed from inside the browser in Inbox (gmail). Using Smart Invert colors and VoiceOver.
I do see the “i’m Not a robot CAPTCHA on this screen.