CStan
I don't think it was so much a case of forgotten lore as it was a case of believing those who had a vested interest in saying so that capirons simply don't work, the design is 'garbage' etc., etc. And the backdrop of all of this is that every book I have on woodworking mentions adjusting the capiron to handle difficult stock. All of these sources from apparently talented craftsmen. I can't find a "hardcopy" source mentioning capirons were crap and not to bother. It appears to me that this was/is totally an internet phenomenon. Those who get or have gotten all of their information regarding planes from the internet can be excused for being confused.

It's not an either/or proposition. Moulding planes are structured to be single-iron. You go with what you have. I don't intend to be guilty of the reverse bias. Single iron planes work. That's doesn't logically extend to say that double iron planes are crap. I think you'll agree.