Pretty accurate. What makes a mountain impassable isn't the height per se - armies can and have operated on very high plateaus. It is the rate of change of height, which makes for impassability and energy-draining climbs. While Spain's mountains, barring the Pyrenees, are never especially high by many standards, Spain has many sudden changes in altitude where you go from flat plains to sharp inclines, as shown by this steepness map of Europe (used for soil erosion purposes now):
Anywhere that is purple on this map is bloody hard to get an army through, unless there are fairly wide passes and the like.