First, I think the forged cranks start out as melt-forgings or other type of castings. Could thes have been made from the castings, left in the stouter, less-machined state to cut costs and compensate for reduced material strength?
The mention of these cranks having dimensions beyond those of Record cranks makes perfect sense to me. These aren't modified Record cranks, but more like the Record cranks are a modified version of these, with machining and possible (but unlikely) additional forging taking away from all the external dimensions. In effect, the record cranks are fully machined and have a lot of material removed in the process.
I don't know of any mystery gruppo, however, that stooped this low, but perhaps some "3rd world" vendor commisioned them during the (very) hard times? This would allow the use of some obsolete tooling that, who knows, might have even been shipped out of the original factory and used at a customer's location. Not the sort of thing anyone at Campy today would want to acknowledge, and maybe no more likely than someone forging (no pun intended) a batch of cranks in Czechoslavakia.
Mere speculations on my part. I agree these cranks have great conversational value! Very interesting.
David Snyder