I think it does account for two motors, though not explicitly. It bases it on whatever number is in the Avg. Energy Use box, and the default number of 11.2Wh/km is a sort of guess at how efficient a dual motor belt drive urethane build will be. The number changes wildly with how you ride (both how hard you accelerate and what road and weather conditions you’re in) as well as the more obvious ones like weight and speed. The lower the consumption number, the better the range, and we don’t tend to break down the per-motor efficiency or anything like that because VESC just reports total draw from the battery so you don’t need to account for that
From what I understand the default number isn’t stupid, it’s neither the worst nor best possible consumption.
For comparison I ride fairly gently (max speed on this board was 25km/h, but no push starts and not trying to baby the acceleration) and on a dual motor belt drive urethane build, at 100kg+ rider weight and an old tired battery that I think has degraded a lot I got 13.5Wh/km.
Speed: Motor Efficiency Discussion - #49 by janpom
Weather impact: Practical range/power consumption testing (serious)
Sorry for the wall of text but one last thing: probably don’t use a 12T motor pulley. The lower the tooth count, the less contact the belt has with it and it becomes far far more likely to get belt skip. I ran 12 for a while and it’s no fun, I was constantly worried about accelerating too hard (I’m not a high power rider at all) and it’s even worse for braking. That and I think it destroys belts faster because they do not like skipping