I would imagine they tuned the map from simulator runs, McLaren are well known for having one of the best simulators in F1 for human in the loop, and computer i

I would imagine they tuned the map from simulator runs, McLaren are well known for having one of the best simulators in F1 for human in the loop, and computer in the loop, testing. It could be that the parameters were slightly off for downforce and grip with their low-downforce Spa and Monza package and Alonso (and the computer) couldn't take Pouhon flat.