I'd have to agree with Tom MacWood that it's a mistake to categorize an architect into a penal vs. strategic category. A better judgement is to look at the ratio of penal vs. strategic. In the case of Donald Ross, I would tend to think that he falls more into the 70% strategic vs. 30% penal.
Based on the few Ross courses I've played in NC and MI (those without major changes..ie. PIne Needles, Mid Pines, Raleigh CC and not places like Oakland Hills), and the reading I've done from books like "Golf has Never Failed Me", Ross' approach favored the golfer that could execute accurate shots, but also embodied the Scottish spirit that believes that golf is not about great shots, but the ability to make great recoveries from challenging locations. I think his Par3s are often considered penal because of the depth of bunkers, but this followed his believe that they should be more difficult since the approach allowed the played to place the ball on a tee and hit the approach from the flat lie (the tee).
If you look at his Par4s and Par5s, the bunkers usually define the paths of greater challenge vs. less risk, and the fairways bunkers have lower lips so that the player has a chance to recover. When bunkers have since been added to both sides of the fairway at fixed distances (ie. Oakland Hills), then Ross' name is often confused with the subsequent architect and hence is considered more penal than strategic.
So don't get caught up in counting bunkers, but rather look at their placement in relation to different playing options, and their ability to allow players to make recoveries if they failed at a previous shot.