The R3 is a twin, so the "R" designation matches.
With 600cc sales in the tank, and looming CARB emissions, the "new" supersport class will be ~650 - 700cc twins. Look at the MotoAmerica twins cup, it was full of MT07's last year. This year it's a bunch of RS660's. Once this R7 is homologated into MA, they'll be a popular bike in that series. If it's being raced in a pro-series championship, then it's absolutely deserving of the R branding.
I have a sneaky suspicion that if this R7 sells well, in a few years we'll see a clean sheet R7 design that's less related to the MT07 and even more aggressive.