Let's be careful about judging manufacturer recommendations regarding crew actions.
It's one thing for a manufacturer to issue technical changes in operation, but quite another to issue recommendations relative to crew behavor. Of course preventive operational recommendations are easy to issue and then to walk away from.
The role of the regulator must be considered first. It is the regulator's job to mandate recommendations according to criticality and effectiveness. This side of it must be examined before deciding on the significance of what Spanair crews did or did not do.
If the majority of MD80 operators really do follow this recommendation faithfully (do they?) then it's a fair question to ask if it was a part of this accident cause and why so?