It's not a function of iFly, per se. It's a function of the NWS (or wherever iFly gets its data). I get persistent green dots near our major RADAR site here in Phoenix. Sometimes it's worst when the RADAR operator sets the elevation really low. (I use animation to show when it's ground clutter.) OR - and this happens a lot near Yuma, AZ - chaff from military exercises gets picked up and painted as precip.
But I agree with you that, generally, when iFly shows green, it's rain. (Unlike Garmin Pilot as of a couple years ago.) When I get around to it, I plan to upload some screen shots comparing iFly NEXRAD to the NWS NEXRAD during Hurricane Matthew.
P.S. In your original post, you said that the METAR made it look like a good day to stay indoors. The METAR looks fine. Did you mean RADAR?