I have given the Smart Control in the new Specialized app a day of testing in a flat area.
Leg 1: Start at 100% batt, set 19.5 km, set battery use 25%, result
Leg 2: Start at 75% batt, set 11.5 km, set battery use 15%, result
Leg 3: Start at 60% batt, set 11.5 km, set battery use 10%, result
Leg 4: Start at 50% batt, set 20 km, set battery use 25%. Result
Battery left 28%, too conservative.
The tendency of being pretty conservative towards the lower charge region could be observed with Mission Control SC, too. I would say the new Smart Control was surprisingly accurate even if the e-bike felt like being assisted with excessive power toward the end of the Leg 1 and underpowered on Leg 4.
The biggest blame I could put on the new Smart Control is the lack of input of the expected Elevation Gain. Let us say you are going on a 50 km ride involving 30 km riding on the flat and the last 20 km would be significant hills. SC would see the Range Trend as positive for the first ride segment, using significantly high assistance. Then, entering the hills, it might be not enough of the battery charge to provide the necessary assistance! Just when you need the most of the boost to be delivered!
I'm starting in a e-bike gravel race this May. It will be a hilly area with 80 km distance and 1,000 m elevation gain. The race rule is to use a single battery and no recharging en route. I might be able to set the Mission Control SC (if the old app would still work in May) but I would not take the risk of being left with a flat e-bike battery in the hills of the Sudovia region, Poland/Lithuania!