I believe if you drive in cold/warm weather or anything other than flat ground the coding is necessary as a safety measure. It helps with engine longevity as well.
2017 model here, the REx makes a quiet little putter. I can't hear it at highway speed.
I do wish they made the REx robust enough for daily use, like the Chevy Volt. I am going on a 600 mile trip and slightly nervous (though the car has been thoroughly checked out).
