Here are some possible explanations:
1. Scorpion might have gotten confused and thought that Mephala had dwarves – this can happen when you restart and get mixed up about which heroes have which creatures, especially if Mephala appeared in a previous restart.
2. There might have been several battles, and they could all have been attacks from a diagonal direction – in that case, the movement points would be calculated as 100 instead of 141... although that seems unlikely.
3. And finally, as I mentioned before, he's tricky – it doesn't depend on the roads, but on the terrain, and it seems to depend on the battle.
There was a task from Anton a long time ago – the map was cleverly designed. You exit the subway and have to attack the guards – if you attack along the road, you won't reach the next point with one step, but if you attack through the rough terrain, you will.