What they failed to mention is what percent of that boost came from autofillers/spammers.
They say they successfully used timestamp/honeypots to keep out spammers; if so, how many spammers did they keep out? If it was tons, then say so, that's useful information. If it wasn't very many, then they didn't need the CAPTCHA in the first place.
I'd be interested in knowing whether the application itself is designed to be immune to autofilled accounts. Assuming people use it to create slideshows they can then share with their family/friends and not socially/crowdsourced a la flickr, a bunch of bots with garbage accounts no one has to look at wouldn't actually harm anyone else's experience of the site.
They say they successfully used timestamp/honeypots to keep out spammers; if so, how many spammers did they keep out? If it was tons, then say so, that's useful information. If it wasn't very many, then they didn't need the CAPTCHA in the first place.