> it doesn't sound that different with the extra diodes.
I can't see why either one is necessary. I wonder if they were left-over from a previous idea, or were over-cautious design. The pair should never do anything, the single looks like unnecessary protection. Like the breadboard was copied to a PCB, then in final testing it was realized that the diodes were probably doing nothing, a waste of 6 cents. In mass production, 6 cents matters. Easy enough to tell the workers to omit them, not worth burning a new PCB mask until the first mask wears out. Since this thing seems to be rare, they probably never wore-out the PCB mask.