Low tire message on 2015 Malibu

I got a message that the right rear tire on my 2015 Malibu was low. I checked it and the pressure was normal. I even brought it up to the recommended 35 PSI. I took it to the shop, and they found a slow leak in the right front tire. They replaced the tire and the message went away. I asked why I was getting a message that the rear tire was reading low. They said something about the fact that I had the tires rotated at my last service. They didn't really explain why I was getting a low tire message on the rear tire when the front tire was the one that was leaking. Can anyone explain this?