As the engines are standardized and the same for each race, IMO, the no gear rule will allow the tuners to better match the individual manufacturer engine's HP and Torque curves. If I remember correctly you want to be at the torque peak as you get back on the gas coming out of a curve. The no gear rule will make this match much easier.
I've heard Robby say in the past that he likes a bigger gap between some gears. He said it allows him to approach each course with more flexibility so he can get more power & speed when and where he wants it, and help avoid wheel-hop under braking. Makes sense. With his road course talent I'd think it'd give him an edge over others.