Tons and tons of webmasters received them and some were scratching their heads as to why. They thought everything was set up properly.
A "rising star" in the Google Webmaster Help forums heard back from Google about the notice where they told him that the message sent out the other day, in some cases, can be ignored. He wrote:
FYI: We've now heard back from Google that this message might sometimes be sent a little bit "overenthusiastically" when there is no real problem. If you're happy you're not inappropriately 301 redirecting one or more URLs to your homepage (either on mobile, desktop, or both), and you're happy you have no faulty redirects or soft 404s (which could be obsolete URLs you're 301 redirecting to the home page instead of 404ing - and which might look like faulty mobile redirects if viewed only on a mobile), I suggest ignore the message. If you feel it's still a problem in a week or two, please do come back and we can take another look for you.
So if you got this message and think Google is wrong, double check and then ignore it if you are 100% confident:
Forum discussion at Google Webmaster Help.