If they can convince people to install Chrome Frame, I'm sure they can figure out how to tell people to enable 3rd party cookies. My guess is they'd have a lot harder time explaining why the user should do that.
And yet they spent all that time doing it ... Seriously, who is Chrome Frame for if not the average user? And they inform you about it as soon as you visit google.com in IE.
I suspect you're right and the uptake isn't what they wanted, but that's not really a valid reason for them to work against the browser settings designed to protect a user's privacy.