The Spanish are most definitely artisans. Give them an H&H or a London spring-opener and they can reproduce them faithfully down to the Self opening mechanism (e.g. The Senior model). It is in the innovation department where they come up short.
As for their inability to produce a viable O/U, it may have come down to economics. The patents were long expired, so they could have easily cribbed a Woodward O/U. They must have tried. I think they could not deliver the equivalent O/U product at a significantly lower cost than the genuine article with the manufacturing methods available to them.
H&H, a venerable SxS manufacturer, was unable to deliver a truly successful O/U design until the 1990's. If they can survive, perhaps the Spanish can repeat the feat.
