Stock – In the exact same state or location as supplied by the original
manufacturer.
So as long as it's in the exact same location it logically satisfies the OR allowance.
That's not strained or tortured, that's how the SCCA chose to define the word stock whether it applied to gear ratios or suspension pick up points on the BSpec Mazda 2. Why didn't they just say "AND" if they wanted it to meet both requirements?
The AMA says this:
Stock - Parts manufactured and delivered by the OEM, which are identical
to the parts installed on the motorcycle by the OEM before retail sale
As to the AMA's stance on ECU's, it varies a bit by class. The S.O.P. with the AMA is all the controlled bits and pieces have to be "as Homologated". Many bits are further restricted by stating the parts must be available to all participants for sale at a price below xxxx delivered within xx days of purchase from any dealership in the USoA. When a part number is superceded the AMA must know about it before it can be used.