My OPEN UP with Enve 4.5 AR with WTB Nano TCS 40s

I am not a very big rider at 5'8" and 135 lbs. I usually run 30-35 Psi. However, when I know that I will be on mostly road (and not gravel), I sometimes run 40 PSI. At this pressure, the Enve AR 4.5 and WTB Nano 40 tires barely clears the seat tube. I was a bit surprised as I've seen people run larger tires than 40s on their UP gravel bikes. I have to assume that they are running 650 b wheels and not 700 cc?? I am not sure if I want to go 650 b at this point. Have thought about the Enve G23 however. Tried them on a demo UPPER bike, and the set up was crazy light!!