The smoothness key has always been rather car-centric. The very_bad category has been defined early in the development of the tag as “needs high clearance”, i.e. it is so uneven that using a normal car, there is a high risk that an obstacle on the road hits the bottom of the car and you need a car with higher than usual clearance to avoid it. I think the “Trinidad” picture you linked to does not show such obstacles and should be moved to the bad category. The other two pictures do show higher obstacles, but not so high that you need a “heavy-duty off road vehicle”. The picture in your post doesn’t show obstacles that could hit the bottom of a normal car either, so I would tag it with smoothness=bad.
Applying smoothness to 2-wheeled vehicles with narrower tires than cars, some surfaces are more difficult to ride on than they would be with a car. We discussed such a surface above and I think your example is another one that is especially rough for bicycles because of the narrow gaps between the stones that are a perfect trap for bicycle wheels. Maybe cyclists (and bicycle routing apps) should learn to expect that the combination of surface=unhewn_cobblestone + smoothness=bad is going to be particularly bad (i.e. very_bad) for them? Or should we tag it with bicycle:smoothness=very_bad?