When displaying a Google login button with React devtools, the following is sent to the browser's console:
Your client application uses libraries for user authentication or authorization that will soon be deprecated. See the Migration Guide for more information.
Also, listed in one of the benefits of the Google Identity Services is "the option to add user sign-in to your site's static content using just HTML". It would be great to implement that as well since I find the Google button takes a second or two longer to load than the Facebook one.