Env: MW 1.30.0 w/ included ConfirmEdit on a public facing site.
Google reCAPTCHA Dashboard warning: We detected that your site is verifying reCAPTCHA passed solutions less than 50% of the time. This could indicate a problem with your integration with reCAPTCHA. Please see our developer site for more information. (https://developers.google.com/recaptcha/docs/verify#api-request)
Doing some testing on my site it looks as though the extension is not sending the required POST to https://www.google.com/recaptcha/api/siteverify with the required values: secret and response nor with the optional value: remoteip (which was enabled in my environment)